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Feature Updates

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1.8 | 1.7.1 | 1.7 | 1.6.2 | 1.6.1 | 1.6 | 1.5.1 | 1.5 | 1.4.3 | 1.4.2 | 1.4.1 | 1.4 | 1.3.1 | 1.3 | 1.2 | 1.1 | 1.0.3 | 1.0.2 | 1.0.1 | 1.0

October 26, 2018 - Stella Architect 1.8

Calibration

Calibration is the process of adjusting model parameters to make the behavior line up with a target, most commonly measured time series data. It is now easy to set up payoffs and use the optimization engine in Stella to accomplish this. Learn More

Importing Time Varying Values

Time varying values allow you to have variables take on different values at different times based on the imported data. This is useful as a mechanism for bringing in a sequence of decisions or controlling values, and also loading in data to be used in calibration. See Import Data dialog box for more details and Defining Calibration Payoffs for the use of imported time varying data in payoff definitions.

Optimization from the Command Line and in Stella Simulator

The -ro option has been added to the command line to run optimizations. See Running Models Using the Command Line for details.

The same option has also been added to Stella Simulator, as has support for sensitivity and more control over initialization. See Stella Simulator Arguments for more details.

Printing of Interface Pages

Print and Print Preview have been added to the File menu on the interface window. These will print the pages currently displayed in the Page Preview Panel. Learn More

Sobol Sequences for Sensitivity

There is an additional option to use Sobol sequences when preforming multivariate sensitivity. Sobol sequences are designed to maximize the exploration of multidimensional parameter spaces. Learn More

Replacing Runs

It is now possible to replace a run with another run so that any graphs or tables referring to the run will be updated. For example if you have a run named base, you can have the current run replace it. Learn More

Units in User Macros

You can now specify the units of measure for a User Macro based on the units of measure of the arguments to the macro allowing full checking of model units. Learn More

New INTERPOLATE Function

There is a new function INTERPOLATE that will take an N dimensional set of points and return the value derived by interpolating between these point values. In one dimension this will act the same way that a graphical would on a vector of numbers. In higher dimensions the interpolation is between planes (or hyperplanes) of the different dimensions. Learn More

Lead-In Time and Restore Inputs Options (Interface)

You can now set runs to start part way into the simulation when working on the interface. This is convenient if you want users to start with some results already available. There is also an option to restore inputs when starting new runs, which is very useful for multiplayer gaming. Learn More

Shape Tool (Interface)

The shape tool makes it easy to add vertical and horizontal separators on interface pages as well as to include outlined or shaded ellipses (including circles) and rectangles. Learn More

Hover Tips in Graphical Inputs (Interface)

There is now an option on Graphical Inputs to display the current x and y values as the user drags the points in the shape. This is especially useful for discrete graphicals. Learn More

Hover Tips on Sliders (Interface)

You can now control when hover tips appear on sliders (always, never, or when the user is dragging the slider). Learn More

Numeric Display Number Formatting

You can now specify number format for the numeric display in the properties panel. This allows you select multiple numeric displays and set the formatting options for all of them together. Learn More

Loop Indicator on the Interface

If you include Loop Indicators on your model they will now be active when the model structure is presented in either a model view or on a story in the interface. Learn More

Simplified Inclusion of CLDs

Causal loop diagrams created in the new CLD Window will now have NAN equations automatically added. These will simplify the inclusion of CLDs in simulating models as they will no longer create invalid equations. The NAN(a,b) format can be added by hand when working in regular models (see Creating CLDs).

Added Mojave Support on Macintosh

Stella will now work with the features in the newly released Mojave operating system on the Macintosh including the dark mode interface selection.

Importing to a Module Maintains Cross Level Ghosts

When you replace the contents of a module using the Import button any cross level connections between the module and the rest of the model will be retained as long as the names in the model for inputs and outputs have not changed. See Module Properties Tab for more discussion or Agent Based Examples for a typical usage.

August 27, 2018 - Stella Architect 1.7.1

Simplified Causal Loop Diagram Creation

You can now ask for a new causal loop diagram and have the simplified toolset necessary for creating causal loop diagrams. That toolset makes the creation and editing of CLDs quick and easy. It also matches the toolset of the Online CLD Editor. Learn More

Switch Color

You can now set the color that a switch on the interface displays when it is on. Learn More

Graphical Input Appearance (Interface)

You can now set the line color for the graphical input on the interface and also specify a fill intensity to display color below the line. Learn More

Integer Option on Allocation Input (Interface)

The Allocation Input object now has the option to computer only integer values allowing more control of both the values and the label appearance. Learn More

Offline Help Files

There is now a menu option to download the help files as a zipped archive for use offline. This allows you to view the help files locally when you do not have an internet connection. Learn More

Sharing Models and CLDs Online

We have added to the options for sharing Models and CLDs online allowing you to give other people access to your work without marking it as creative commons. This option is not available in the free online editor. Learn More

Causal Lens Improvement

If there are long variable names in the causal lens, you can now Hover over to see the full expanded name. Learn More

Multiple Leakage Control

When a conveyor has multiple leakages with different leak zones you can now specify whether the leakage fraction on later leak zones applies to the inflowing quantity or the quantity that has remaining after the earlier leakages. Learn More

July 30, 2018 - Stella Architect 1.7

Navigation Control

The Interface has a new tool used to add a set of navigation links to an interface page or template. The bar of navigation links can appear as a row of tabs or buttons. The styling includes radius corners and spacing. Learn More

Spell Check

You can now spell check for variable names, documentation, and labels. You can select different dictionaries in the Preferences Dialog and correct misspellings using the Context Menu.

Encapsulating Sectors and Selections into Modules

There is new functionality to take a selection of variables, or a sector, and create a module with the appropriate cross level connections into and out of it. This makes it easy to simplify models that have too much detail built up in any given module. Learn More

User Defined Macros

You can now create reusable pieces of model structure that can be used the same way that the builtin functions are. This allows you to create customized versions of commonly occurring patterns such as cascaded delays as well as more specialized functions. Learn More

Bubble Charts

Bubble charts allow you to display three different dimensions of attributes on a single graph. These graphs represent a snapshot of values at a time and will animate during simulation or when dragging the time slider. Learn More

Mixing Graphs and Tables in Containers

You can now create a container that includes both graphs and tables making it easier to provide the output you want without using up real estate. See Graph Series Property Panel and Table Properties for more details.

Run by Modules Improvements

It is now possible to turn modules on and off in Stella Live, while paused. Learn More

Conveyor Leakage Changes

Leakage computations on conveyors with a variable transit time have been improved to more accurately reflect the leak fraction or rate. Learn More

Interface Scaling Improvements

You can now set interfaces to scale prepositionally when they are deployed. This makes it easier to have interfaces that work on different devices without having to limit the minimum or maximum size (another added scaling capability). See Resizable Interfaces and the Resizable Options dialog for more information. Learn More

Multiple Entry Scatter Charts

Scatter charts can now have more than a single entry. This allows for comparison of x and y values across different runs or comparison of different sets of x and y values. Learn More

Irregular Time Axis on Imported Data

It is now possible to import data with arbitrary time values rather than requiring a uniformly increasing time axis. This makes it easier to accommodate missing values as well as values from different data sources. Learn More

Stashable Graphs and Tables

Stashable graphs and tables allow you to hold on to run results that are of special interest, while displaying the current run at all times. This is a convenient way to collect a sequence of interesting outcomes, and replaces the old functionality related to persevering and releasing data. Learn More

Picture in Picture Module Viewing

It is now possible to peek into modules without navigating into them. This allows you to see what is happening in a module while still looking at what is happening on the parent model of that module. This allows you to make changes in Stella Live and see the consequences of those changes in another module. It also allows you to get an overview of module structure without losing your current visual focus. Learn More

Model Compare

A new feature has been added that allows you to compare the model you currently have open with another saved model. This is a convenient way to see what changed have been made for models derived from one another or a common source. Learn More

Narrowing Time Range for Results Panel and Causal Lens

You can now zoom in on the displayed time in the Results Panel and Causal Lens. This makes it easier to trace down sources of behavior at a point in time, as well as seeing changes in behavior between multiple runs. See Results Panel and Causal Lens™ for details.

Vertical Sliders

There is now an option to display sliders vertically as well as horizontally. Learn More

Collapsable Panels

Many of the panels now include sections that can be collapsed if you do not needs to refer to it. This decreases the amount of information displayed on the panel and thus easier to work with. Learn More

Equation View Enhancements

We have added options to the equation viewer to make it easier to provide written model documentation to meet the requirements of peer reviewed journals such as the System Dynamics Review. Learn More

Line Graph Updates

You can now specify that graph be drawn without connecting the points into line. Learn More

Button Highlighting on Mouse-Over (Interface)

There is a new option to have buttons change their appear as the mouse cursor passes over them. Learn More

Aligning Objects

When you select 3 or more objects on the interface there is now a menu option to either align or distribute those objects to clean up layout. You can keep the movement of objects completely horizontal or completely vertical by holding down the Shift key. This works on both the model and the interface. Learn More

Loop Indicator Improvements

The loop indicator now works by selecting all of the elements you want highlighted. This allows you to select more specific loops or parts of structure for display. Learn More

Find Persistence

The find will now retain what you are searching (Variable Name, Equation or Documentation), the order in which to display results, and whether to search in the whole model, the current module or the current module and modules it contains.

Sensitivity Improvements

You can now provide an external list of parameters to change when running sensitivity analysis, and we have changed the sampling for Ad-Hoc and Incremental when running a limited number of runs to better support random selection of discrete values. Learn More

Improved Security Settings

We have made a number of internal improvements to the security settings and fixed issues that arose from specific character combinations in low security passwords. One consequence of this is that models saved in the current version using security settings will not open in versions before version 1.7. Learn More

Improved Opening Time

Large models should now open more quickly.

April 16, 2018 - Stella Architect 1.6.2

Optimization within Sensitivity

In addition to being able to run optimizations over sensitivity runs you can now run an optimization within each sensitivity run. This is a convenient way to see how the optimal parameters found vary based on other model parameters or noise seeds. Learn More

Constraint Handling in Differential Evolution

It is now possible to add constraints to differential evolution optimizations allowing the specification of inadmissible search spaces without degrading the efficiency of the search. Learn More

Find Options

The find tool now makes it easier to look for content that appears in equations and documentation by allowing you to specify search terms within these. Learn More

Managing Time Formats

A Manage option was added to the right click (Ctrl-click/⌘-click) menu item for formatting items in graphs and tables. This will open the Manage Time Labels dialog box allowing you to add and modify formats as well as changing the default time format. Learn More

Table Position in Results Panel

The scroll position on the table in the Results Panel is now retained when moving between variables.

Documenting Models in the Equation Viewer

Options have been added to the Equation Viewer to make it easier to create model documentation that meets your needs. It will now display optional variable usage and provides increased control over annotation. Learn More

Sketchables with Fill

You can now fill in the area underneath a sketchable graph. This is especially useful when using area graphs.

Getting Outputs in the Sensitivity Parameters List

There is now an option to see both the inputs to each sensitivity run as well as the outputs in the currently displayed graph or table. Learn More

March 16, 2018 - Stella Architect 1.6.1

Ghost Tool

If you click on an empty part of the model when using the ghost tool the Find dialog will come up allowing you to ghost a variable without first navigating to it.

Restore Window Layout

Under the Window menu on the model and the interface, the Restore Window Layout option will reset all window, panel and tool bar positions to where they were when Stella was first installed (isee systems default settings). Learn More

Zoom to Fit

In the Zoom control, a new option has been added to automatically adjust the zoom level of the model diagram or interface page so that all objects will be visible within the viewable space without needing to scroll. Learn More

View Results and Causal Lens

A combined View Results and Causal Lens has been added to the Online Model Editor. Learn More

February 15, 2018 - Stella Architect 1.6

Global Number Formatting

You can now specify a model level default number format that will be applied to all variables instead of having to do this variable by variable. This is done in the Model Settings Properties Panel. The options are the same as they are for each variable, and variables can still be set individually as well. Learn More

Currency, Prefixes and Suffixes for Formatted Numbers

Instead of limiting output formatting to use a $ or % you can now specify arbitrary prefixes and suffixes for output numbers. Learn More

Time Formatting and Labeling

You can now format time to display years, months and days and not simply decimal values. Learn More

Variables Used in Graphs, Tables and Interface Objects

You can now find what graphs or tables (or interface object) a variable is used in by right clicking and selecting Find Uses on the right (Ctrl) click menu. See Context Menu for more details. You can also locate exported tables from the Export Data dialog box.

Published Model Performance

The performance of published models, especially simulation speed, has been dramatically improved and will, with a modern browser, match the performance on the desktop.

Importing and Exporting Data

It is now possible to import and export data from the interface for published models. These are both set up using a Button (Interface). When the button is clicked the user will be prompted for a file to upload or save to. Only .csv files are supported on the interface. See also notes in Creating Import and Export Files.

Simulation Speed Control

The new Simulation Speed control allows you to let the interface user set the speed at which the model simulates. Learn More

Object Visibility

You can now have objects be made conditionally visible based on variable values, or the role in a multiplayer game. This allows customization of the user experience based on the state of a simulation. Learn More

Display Time

Much like the progress bar in the development environment the Display Time object shows progress during a simulation and allows the user to scrub over different times in the simulation. Learn More

Support for Sound

You can now add a button that will play a sound, and have a sound be played in response to a simulation event. This works the same on the desktop and for published models, though supported sound formats vary by browser. See Button (Interface) and Simulation Event Action dialog for more detail.

Documentation on the Interface

You can now display equations, units of measure, and any documentation provided for a variable in a Model View. This material is displayed as the mouse moves over the elements of the model. Learn More

Negative Binomial Distribution

The NEGBINOMIAL (negative binomial) builtin has been added. This returns the number of failures that occurred getting to a specific number of successes for a given probability of success. Learn More

Truncating and Sampling Distributions

You can also specify a minimum, maximum and sampling interval so that it is easy to create truncated or sample distributions in models, and truncated distributions for sensitivity. Learn More

Quoting of Array Dimensions and Elements

You can quote an array dimension name and element names by putting double quote around them (as in "1-2"). This capability is in place primarily to support the importation of models translated from other languages. If you do create labels with quotes the model will not work in previous versions of Stella.

Probability Density Options on Histograms

The Histogram has had options added to appear as a probability density function (pdf) and cumulative density function (cdf). Learn More

Improved Variable Highlighting

Highlighting of variables is now easier to find even in dense models with lots of color.

Passing Parameter Information for Data Collection

It is now possible to pass parameters to a simulation set up with data collection by appending them to the URL for the model. Learn More

December 12, 2017 - Stella Architect 1.5.1

Flight Sim

The behavior of models running in Flight Sim mode has been modified so that they respond continuously to input changes rather than momentarily pausing. Learn More

Parameter Control Panel

The functionality to create an import file from the Parameter Control panel has been updated to only save values that are changed. This will allow you to easily create import files based on optimization results and also to create an import file that captures a snapshot of the interface input control settings. Learn More

Context Sensitive Help

Context sensitive help is now available in most dialogs as well as the properties panel.

November 21, 2017 - Stella Architect 1.5

Optimization

Optimization allows you to find a set of parameter values (model constants) that maximize a payoff you defined in terms of other model variables. This is similar to running sensitivity that is guided to achieve specific outcomes. Learn More

Confidence Bounds, Histograms and Correlation Plots

The output of graphs and tables has been enhanced to support a number of formats that can be very helpful when working with a large number of sensitivity runs.

Confidence bounds allow you to see what percentage of runs leave values in different ranges at each point in time. This allows for a clear visualization of the divergence or convergence of values over time given different assumptions on parameters and also how concentrated the values are at any point in time. See Graph Series Property Panel for details on turning these options on. The same information can be presented in tables identifying numeric values for the different percentiles (see Table Properties for details).

Histograms are created by collecting results from different runs and grouping them into buckets for different ranges. This allows you to see how many runs fall into each of the ranges. Histograms are available as an option on the Bar Graph. Learn More

Correlation plots allow you to see how one variable correlates with another over a series of runs. This is done with scatter graphs by turning on comparative and checking the option to show only a single value. Learn More

Precomputed Values

When a model is paused, the values of all variables, stocks, flows and converters, are available at the time of the pause. On the model window these values will be updated if you make changes to any model parameters. For tables and graphs, the interface will report only stocks at the current time, but other output devices, such as numerical displays, can be set to report the precomputed values. The option to pause before computing flows has been removed as this is no longer necessary. Learn More

Sensitivity, Payoff and Optimization Setup

These are now accessed through the model analysis tab of the properties panel for the model. Use the sensitivity tab to access sensitivity setup. Learn More

Context Sensitive Help (not in rc1)

Clicking on the ? icon in any of the panels or dialogs will now take you to the help entry specific to that panel or dialog.

Save Interval

You can now specify a save interval. This is useful for decreasing the storage requirements for large models and also for keeping data collection working well. Learn More

Graph and Table Labeling and Ordering

If you are using the tabbed or dropdown styles for selecting between multiple graphs you can now set a label for the tab or dropdown entry that is separate from the graph/table title. It is also possible to reorder the entries. See Pages Styles (Interface), Graph Settings Properties Panel, and Table Properties for more discussion.

September 29, 2017 - Stella Architect 1.4.3

Keyboard Shortcuts

You can now use keyboard shortcuts to select tools when building models. Select the Stock tool with "Ctrl/Cmd + 1" and so on. Learn More

September 22, 2017 - Stella Architect 1.4.2

Graph and Table Pad Labels

You can now rename the graph and table pads that show when the graph or table is minimized. Editing works just as it does for variable names.

Annotation Button for Variables

You can now use the annotation button to display a variable's documentation, equations and units of measure. Learn More

Graphical Panel

The units of measure now appear in the graphical panel - making it easier to there are units issues with graphical functions. Also, if the equation for a graphical has an error the panel will open on the equation instead of the graph.

Interface Page Resizing

When setting interface page size, existing content may restrict how much it can be adjusted. If a page has content that would be outside the page on resizing you will not get a message indicating the reason the page size was not able to be changed as requested.

July 10, 2017 - Stella Architect 1.4.1

Loop Label

A new Loop Label object has been added to the mode editing toolbar. This allows you to label loops and will highlight the links in the loop when the mouse passes over it. Learn More

Navigation on the Model

A new navigation button has been added to the model to allow position changes to predefined locations or variables. These can be useful as shorcuts for navigating through large models. Learn More

New Builtins

Use NAN to set a variable value so it will not appear on graphs. Use CLOCKTIME to return the current time on the computer the software is running on. Learn More

Graphics Frame on the Interface

There is now an option to fit the graphics content to the frame. Learn More

July 22, 2017 - Stella Architect 1.4

Multiplayer Games

In addition to publishing model interfaces, you can now create multiplayer games in which players connect from their own browsers, make decisions, and indicate their readiness to proceed. The model then uses decisions from all of the players as inputs for the next step in the game. Multiplayer games can be published to the isee Exchange under the Creative Commons license, with some limitations on model size. Learn More

SVG Animations

It is now possible to create sophisticated animations based on SVG graphics files. These animations can include color, size, and rotation. Learn More

Conditional Actions on Buttons

When you add a button to your interface, you can now set conditions under which each of the actions will be executed. This is especially useful in multiplayer games. Learn More

Resizeable Interfaces

Published interfaces can now be made resizable, allowing them to work well on a variety of devices. Learn More

Data Collection

You can now collect data on the use of your published simulation, including the results from different users and the time spent on different pages. Data collection is available through an isee Exchange subscription. There are several reporting options available for analyzing the data. Learn more .

Array Expressions

The modeling language has been extended to allow the use of expressions inside of the array functions (such as SUM(a*b)) to take an inner product. An inner product operator has also been added for 1 and 2 dimensional arrays. See Working with Arrays and especially Specialized Array Manipulation for more discussion.

Multiple Page Graphs, Tables, and Inputs (Interface Only)

Here are new options for navigating through multiple pages of graphs, tables, and input devices. Rather than the standard right and left buttons, you can use tabs for each page, or a dropdown list including all pages. This is applicable to graphs, tables, group inputs, and arrayed inputs, and is selectable from the properties panel for each. Learn More.

Connecting Modules

When you connect a variable to a module, or a module to a variable, you will see a menu item allowing you to select which variable within the module to connect. This will appear only if there is something marked as an input or output within the module that has not yet been connected.

Using Initial Equations with Graphical Functions

We have made a behavior change when you are using a separate initialization equation for a graphical function variable. Previously, the I equation would determine the value of the variable. Now the I equation determines the input into the graphical function.

Initialization and Graphs

Graphs will now use the initial values computed in the background. For bar graphs and pie charts, this means they will be populated with initial values before and after running an output restore. Regular graphs will not draw, but they will have a scale. This is true for models and interfaces, including published interfaces. Note that changing a controlled value will no longer generate a new initialization.

Stella Live Behavior

We have adjusted Stella Live to be less sluggish on larger models, and also to give visual cues when the model is in the process of computing. In particular, as you dial a knob, while the software is computing the graphs, over model elements will be displayed in gray instead of red. This indicates that the graphs are potentially out of date relative to the value showing for the knob.

June 12, 2017 - Stella Architect 1.3.1

Model Editing

If you try to make a connection that would cause a circularity the list of variable involved in the circularity is not displayed in a dialog box.

Hovering on a connecter into or out of a module will now show which variables are being connected.

You can now navigate out of modules using keys. To get to the containing module use Ctrl+Up Arrow (⌘+Up Arrow on the Mac). To get to the home module use Shift+Ctrl+Up Arrow (Shift+⌘+Up Arrow on the Mac). Learn More.

The three line limitation on variable names has been removed.

You can now add polarity symbols to flows.

Interface Editing

On the interface, the auto-alignment grid now includes objects in templates so that you can more easily manage page layout.

Keyboard scrolling using the arrow keys has been improved.

Equation Editing

Array names and elements have been added to the auto-complete when working with arrayed equations.

The scales and ranges tab has a new icon (#) that is more representative of its function.

Published Models

We have substantially improved the performance of published models of significant size.

May 10, 2017 - Stella Architect 1.3

Stella Online

You can now edit and work with your models online by logging in through the isee Exchange. Learn More

New Graph Options

Available for both the model and interface we have added two new options for displaying results. The Pie Chart is a new output format for the display of variable values at a point in time. The Area Graph allows you to display a series of graph values stacked on one another with distance between them based on the values of the variables. Both of these are configurations of graph objects and can be selected in the Graph Properties Panel.

Allocation Input on Interface

The new Allocation Input (Interface) object allows users to set values for inputs that need to add up to a set amount. It is implemented as a draggable pie chart, with adjacency determining the sequence in which other inputs change as the user makes adjustments.

Reset Buttons on Interface

A reset button has been added to interface input objects allowing them to be reset to the model value by the user (the button also marks the control as changed). This option to use this is set in the Interface Settings Properties Panel.

Import/Export Now action on Interface

Buttons on the interface can now execute either an import or an export of an on demand data link. These actions do not do anything for published models. See Button (Interface) for more details.

Graphical Input Points

Graphical input objects on the interface can now be changed either by tracing the shape, or by switching the Table view and entering xy pairs. Learn More.

Improved Import and Export Capabilities

You can now import both the x and y axis for graphicals by putting :x and :y after then name of the graphical in successive rows or columns. See Creating Import and Export Files for details. The import options now handle arrayed inputs more consistently and better manage compatibility between US and European number formatting.

Parameter Control Panel Improvements

The Parameter Control Panel now highlights variables that have been overridden on the panel making it clearer what has been changed (this is especially important for values already imported).

Language Changes

Any graphical functions that use a constant as an input will now be marked as invalid. This makes it easier to uncover issues where TIME might have been the intended input. If you do want a constant as an input you can use an expression (as in 0+0) to prevent the error. The INIT and ENDVAL builtins can now take an expression in addition to using a variable directly.

February 1, 2017 - Stella Architect 1.2

Updated Data Manager

A number of other improvements have been made to the Data Manager giving you more control over the way in which runs roll off the list and what runs are displayed in graphs and tables. Learn More

Importing External Runs

We have added the functionality to import runs from external data sources to the Data Manager. This makes it easy to compare results with measured data or with results from other models. Learn More

Parameter Control Windows Updates

The parameter control window has been enhanced so you can see the original model value and to make it easier to reset and control different variables. Any variables appearing in the parameter control window are also marked on the model diagram.

Model View Improvements and Animation

You can now optionally animate diagrams shown in the Model View including those shown for storytelling. The Model View controls have been improved to make it easier to include model elements on interface pages and stories. Learn More

Circularity Checking

Circularity checking and reporting have been improved and now detects subtle initialization dependencies related to leakages and discrete stock equilibrium initializations. Circularities are now reported one loop at a time, and all the variables in the loop are marked invalid making it easier to visual the loop.

Divide 0 Operator

We have added a // operator which works the same as SAFEDIV giving 0 instead of an error when dividing by 0. Divide by zeros are more accurately reported, even when they occur within expressions such as MIN. Legacy models will automatically have some of this reporting masked to maintain compatibility.

Preserving Graphs and Tables

You can now preserve graphs and tables with a single click so that they will not change with new runs or be cleared when you restore outputs. This is done from the Graph Properties Panel. Learn More

June 20, 2016 - Stella Architect 1.1

Interface/Stella Designer

The interface development tools are all new. The new interface development and deployment capabilities take you from design to presentation and, optionally, the web quickly and cleanly. Learn More

Interfaces developed in previous versions of the software will be translated and most of their functionality retained, though some adjustment will be necessary to get optimal results. Learn More

Causal Lens

The Causal Lens displays graphs for a variable and the inputs to that variable helping you to better understand the sources of model behavior. Learn More

Table in Results Panel

The Results Panel now includes both a graph and a table allowing you to look at specific values at specific times easily. There is also a checkbox to not round the scales which is helpful when looking at variables with limited movement through a simulation. Learn More

Simulation Log

The Simulation Log records any variables that go above or below their specified ranges, as well as graphicals with inputs above or below their specified minimum and maximum x values. The same log is also used to report messages about anything that happens when opening a model. Learn More

Parameter Control

The Parameter Control Panel allows you to see what variables are changed relative to their model equations, and also make changes to those variables. Learn More

Selection History Panel

The Selection History panel keeps track of which variables you have selected making it easier to go back and see where you have been. Click on an entry till take you back to that variable. Learn More

Clearer Selection Highlighting

We have improved selection hightlighting to make it easier to see which variables have been highlighted. This is especially useful as we have added a number of new ways to navigate between variables.

Causes and Uses in Equation Panel

You can right click on a variable in an equation and jump to that variable. There is also a Causes/Uses menu to navigate to variables that cause, or are used by the variable you are looking at. Learn More

Improved Error Messages

We have improved the error message reporting in equations and made this reporting somewhat stricter, especially around the MIN and MAX functions, to prevent ambiguity.

More Informative Units Messages

The units messages now tell you have many variables you have left to define units for. If you have not defined units for any variable, the dropdown simply reads Define Units.

Unrestricted Naming for Variables

There are no longer any restrictions on what names you use for variables, except that they must be unique and not conflict with any Builtins. When used in equations variables that have operators or other characters will be quoted and escaped. (If you type them in you will need to do this, but it happens automatically if you choose them or use autocomplete.) Variables with a period (.) in them will also be quoted when displayed on the diagram (this is to prevent confusion with module qualified names).

Improved Speed

Models open significantly more quickly than before letting you get on with development. Exporting of data is significantly faster and will happen in parallel during simulations.

Added PROD Functions

An analog to the SUM function takes the product across elements of an array.

Large Model Use

An option has been added to the Preferences Dialog that turns off Stella Live when in Explore mode. This allows you to work with larger models and make changes on the model window but only simulate them when you explicit request a run. Learn More

Run Specs always Available

You no longer need to go to the home module to change run specs or other model wide settings. These are avilable in the panel from any module.

Equation Viewer

You can now order equations by sector and also view values in the Equation Viewer. Complete information about model size has also been added to the end of the equation listing. Learn More

Simulation Events

We have redone what used to be called Posters or Simulation Messages into an easier to use system of Simulation Events that can be applied separately to the model and interface. Existing models will have these converted to the new format working on the model. Navigation events will need to be redone. Learn More

Export Formats

We have added new export formats to export a single set of values or values at a time and improved the way tables are specified for exporting. Learn More

December 8, 2015 - Stella Professional 1.0.3

Integration with High Resolution Displays

Version 1.0.3 is designed to work well with high resolution displays, including Retina displays on the Macintosh. The icons on the screen will automatically be enlarge to accommodate displays with high pixel counts and the diagrams will be presented so that it is easy to read at default zoom levels.

Updated Icons

We have updated the icons used throughout to be clearer and more consistent in addition to working better on different resolution monitors.

Edit Explore Transition Changes

The movement back and forth between Edit and Explore modes has been streamlined. Changes you make to constants in explore mode by adjusting knobs or entering values in the Results Panel will persist if you enter Edit Mode and then go back to Explore Mode. Modifying an equation will reset any value you set in explore mode, but only for that equation.

Enter values for arrayed constants in the Results Panel

You can set values for arrayed constants in the Results Panel in explore mode (arrayed constant do not have adjustable knobs). Just open the results panel and click on the constant you want to change. You can select the array entry to change from the dropdown at the top of the results panel.

Increment setting for constants

Constants now have an increment setting that can be used to control the number of values they will take on when changed via a knob in Explore Mode. This can be very helpful if you want to limit the number of values that a constant can take on, and will even allow for the addition of switches that take on only 0 and 1 as values. The increment is set in the Scales and Ranges panel.

October 12, 2015 - Stella Professional 1.0.2

Importing Temporary Changes

This functionality has been moved to the Panel to make it easier to use. Rather than opening the import dialog, open the Properties Panel on the model and there is a new tab to make temporary changes, including importing interface settings from STELLA and iThink Version 10.1.2 models.

Graph and Table Creation

Clicking on the add variable button in the graph and table panels will now open up the Find dialog making it easier to select and add variables.

Improvements to Copy

Copying model diagrams into the clipboard is now more sensitive to context and will remove the borders from graphs when they are copied by themselves. This makes it easier to paste your content into other applications.

Map/Model view stored with model

Now when opening a saved model, it will open in the same view in which it was saved.

August 6, 2015 - Stella Professional 1.0.1

Speed

Substantial improvements have been made to Stella Professional's computation engine. Not only will models open more quickly, but large models should simulate three to eight time faster than in the previous version. This allows you to get more done more quickly.

SAFEDIV

A new function SAFEDIV (<numerator>, <denominator>, [<onzero>]) has been added that allows division in cases where the denominator might become 0. When this happens the function will return 0 or the optionally specified third argument. Use this to prevent simulations stopping because of a divide-by-zero condition. Learn More

Importing Temporary Changes

The Import functionality has been enhanced to allow you to import values without making any changes to model structure. This is useful for running experiments in which you do not want to change the model, but just see the results of changing constants and graphical functions. This also allows you to override computed variables with a constant value, much like you would when, for example, attaching a slider to a converter on an interface.

An option has also been added to the Import dialog that will read interface control values from a model created in version 10.1 and create a temporary change files. This allows you to simulate models in Stella Professional and get the same results that they generated in the Version 10 products.

Repeating Build Steps with the Alt Key

The Alt key now works by holding it down, rather than tapping it, when you want to repeat a build step such as drawing connectors between variables.

Clear Highlighting of Connectors and Names

When you position the mouse over a connector handle (or arrowhead) the color of the connector will change to indicate that it is active and can be dragged. Similarly when you position the mouse over a variable name, the name will be highlighted with a box to indicate it can be repositioned. This makes it much easier to adjust model layout, especially for densely connected models.

New Menu Items

A Windows menu has been added to allow you to more easily navigate between models when you have multiple models open. Under the Windows menu is an item to open the Results Panel. A Run Specs menu item has been added to the Model menu as an alternative way of opening the Run Specs panel.

Registration Dialog

Registration information can now be accessed and changed through the Registration dialog box opened from the Help menu. This allows you to change your registration information and unregister the software from one computer, so you may use it on another. Learn More

Delay Marks and Lettered (s/o) Polarity

When you place a connector the Style Panel will contain an option for a Delay Mark. The polarity markers can be shown using either +/- or s/o as specified in the Model Settings Properties Panel.

Hide Module Prefix Option

Set this on the Model Settings Properties Panel to shorten the names displayed in graphs and tables (eg. have profit be displayed instead of accounting.profit). Learn More

Sketchable Graph Enhancement

You can now create a Sketchable graph for any graphical function in the model without needing to add another variable for comparison. This allows you to use the Sketchable graph as an input control. Learn More

March 26, 2015 - Stella Professional 1.0

The Stella Window

While using the same set of building blocks and supporting you step-by-step in maintaining the integrity of the models you build, you now have more flexibility and control over appearance. You'll also find powerful new ways to work with and understand your models.

New Toolbars

For previous users, Stella Professionalis both very familiar and very new. The first thing you notice is a new set of toolbars.

Build Toolbar

The Build Toolbar contains the same components as previous versions, with slightly different icons. By default it is in the same location.

Moving Toolbars

All toolbars are movable and can be docked on any side of the window. By default, the Build and Mode toolbars are at the top, and the Run toolbar is at the bottom. If you grab the handle at the left end of a toolbar, you can put the toolbar in a new location along one of the other edges, or leave it floating.

Panels

Side-docked panels allow you to define and edit properties for model entities while still viewing the diagram. Drag and drop entities from the diagram into equations to use them as variables. Undock the panels to create a floating window that you can resize and place anywhere on your screen. Learn More

Layout

In addition to fonts and colors you can now set the size on stocks and converters and set specific Converters to be name-only. This, combined with bendable Bezier connecters, allows much more flexibility in presentation. Easier layout is facilitated by Object guides. These appear as you move objects around the window, any time one object aligns with another.

Styles

You now have much more control over appearance. Set fonts, colors, and other attributes. For example, you can change the font on flows, mark a converter as Name Only, resize stocks, and use Bezier connectors

Model Hierarchy

Run Specs and Page Settings follow this heirarchy, and are set from the Properties panel. When in the root page of the model, with nothing selected, set the Run Specs and Page Settings for the entire model. If you create new modules, they inherit those settings, but you can override them for any module. Any modules used within that module inherit its properties, but they in turn can be overridden.

Partial Simulation

Use Partial Simulation tab to select specific modules or sectors to include in the simulation.

Page Settings

Use the Model Styles tab to set default fonts, colors and label positions for all objects for which those attributes have not been set.

Run Specs

Models use a hierarchical structure. Set styles for objects at the model level and override them at the module or object level. Change the model style to changes everything that has not been explicitly overridden. You can also change styles and other attributes for all selected objects.

Multi-dimensional arrays

Expanded array capabilities provide more flexibility when you are defining array equations, creating arrayed graphical functions, and entering constants across an array. Create up to ten dimensions for arrayed entities. Index dimension elements by number or label. Use the new Array Editor to easily import or paste element labels from a spreadsheet or comma/tab-separated list. Learn More

Data Manager

The new Data Managers allows you to archive and recall simulation results. Name and save run data from different scenarios or sensitivity tests to easily identify and reload results. Simulation data is stored in a separate SQLite database file and accessible using standard database tools. Learn More

Embedded modules

Hierarchical modules are now embedded in a single model file by default. For collaborative model building and creation of reusable templates, use the option to automatically save modules as separate files. Learn More

Statistical built-in functions

COMBINATIONS, FACTORIAL, INVNORM and PERMUTATIONS have been added to the list of statistical built-in functions. New stochastic distributions include BETA, BINOMIAL, GEOMETRIC, GAMMA, LOGISTIC, PARETO, TRIANGULAR, and WEIBULL. To learn more, see Statistical builtins. Learn More

Rich text documentation

Source information and other details about model entities can be documented in rich text/HTML format, using options available in the new Documentation panel. Learn More

Improved conveyor leakage

Conveyors now support multiple leakage flows. Use additional leak zone options to simplify main chain structures that contain cohorts with varying leakage fractions. Learn More

Expanded Find functionality

Use the new Find palette to locate model entities using string search, hierarchical views, and filtering capabilities. Drag and drop entities from the Find palette directly into entity equations and input/output devices. Learn More

New graphical function options

Edit the input values (X-axis) of graphical functions to align with your data. Use the new continuous extrapolation option to linearly extrapolate values that are beyond the graphed curve. Learn More

Industry standard XMILE format

Model files support the new industry standard (XMILE) for common interchange of system dynamics models. Use any text or XML editor to search, edit, or document your model. Learn More

More powerful modeling engine (STEAM)

The new STEAM engine does not place limits on the number of entities, data points, and/or time steps in your models. This new more powerful and flexible engine will provide a solid foundation for future development and expanded functionality of Stella.

Cycle Time

Cycle Time lets you time stamp and track material as it flows though the model in order to precisely compute how long different tasks and activities are taking.

Delay Converters

Delay Converters lets you mark a Converter as changing over time in response to changes in its input as happens with SMTH1, SMTH3, DELAY, DELAY3 and related Builtins. A Delay Converter shows a box inside the regular Converter circle indicating it has some of the properties of a Stock. Because it has properties of a stock it is possible for Delay Converters to be involved in feedback loops in which no explicit Stock exists.

Units

Units are more flexible and comprehensive and provide better feedback on issues in dimensional consistency. It is now possible to define multiple aliases for a unit of measure so that you have more flexibility in expressing compound units.

Sensitivity

Sensitivity now allows for a broad range of distributions in specifying input changes.

Module Files

Module files are now stored in a folder prefixed with the model name so that you can save a separate copy of a model using modules in file without changing the original model.

Find Dialog

Find dialog has been updated to provide much better control for searches including finding remaining Building Block errors.

Random Number Generator

New Random Number Generator provides more robust streams of values for the different random number Builtins. The new generator is appropriate for use with high replication Monte-Carlo.

Built-Ins

New Builtins have been added, primarily to support Cycle Time (CTFLOW, CTMEAN, CTMIN, CTSTDDEV, CYCLETIME, THROUGHPUT) but also UNIFORM for random number generation and GAMMALN for statistical computations.

Arrayed Equation Editor

Arrayed Equation Editor for non Apply-to-All arrays makes it easier to work with arrayed variables that have multiple equations. You can pop it up from the Equation tab of the Properties panel and select multiple element entries to edit together. This makes it much easier to work with arrays where many of the equations are the same.

Explore Mode

Enter Explore mode by running the model from the Run toolbar or menu, or select Explore from the View toolbar. In this mode, graphs appear on all objects for which results are available. To view larger graphs, including full axis labeling, open the Results panel and select an object containing a graph. This allows you to easily walk through a model with the mouse looking at results. Open the Results panel from the Model menu or right-clicking an object and choose View Results.

Edit Mode

Enter Edit mode by double-clicking a model element while in Explore mode. All appropriate tabs appear for the selected object.

Validity Indicators

The validity mechanism evaluates equations and units for validity and dimensional consistency. In Map view, any unfinished or invalid building blocks contain a small caution sign.

Results Panel

The Results panel shows comparative graphs on-the-fly. You can still define and place Graphs and Tables in the model with these added capabilities to graph any selected variables from selected runs, include comparative and non-comparative results in a single graph or table, use the Properties panel to control scaling, layout and appearance and Ctrl-Drag (Cmd on Mac) building blocks onto output devices to populate Graphs and Tables. You can even use this method to populate equations, summing converters, and any input variable.

Comparitive Graphs and Tables

Comparative tables and graphs now work in concert with the Data Manager. Any runs held by the data manager are displayed in Comparative graphs and tables as soon as you specify the variable. Thus you do not need to run the model again to see the results when you change a variable. If you have specified that 5 runs be saved in the Data Manager, the oldest run falls off of Comparatives when you make a sixth run. When doing a Sensitivity run, Comparative graphs and tables show the results for all of the Sensitivity runs, but once you make another run, they revert to showing the runs stored by the data manager (which may be a smaller number of runs). You can now lock individual runs in graphs and tables. This can be done on the Property panel for the graph or en-masse for Comparatives by right clicking and accepting the list of Displayed Runs other then Next Run.

Looking for more release notes?

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