In Vensim 7, we’ve combined real-time Synthesim with sensitivity analysis, so you can see the distribution of outcomes from Monte Carlo runs interactively. This is great for giving users an appreciation of the risk associated with a decision, rather than just a best guess.

]]>Vensim can be used to put big data in context, by incorporating the learnings from big data in simulations that account for organizational structure and finances. Vensim can also do data intensive simulation, with flexible I/O, advanced algorithms for calibration, optimal filtering, confidence bounds and Monte Carlo simulation.

]]>The model is: discrete 1.mdl

Here’s a followup, incorporating random processes:

The model: stochastic 1.mdl

And finally, a more practical example that puts it all together:

The model: lemonade 1.mdl

]]>The purpose of this video is not to discuss the mapping of the world models to the real world, though that is of great importance to everyone. Instead, we take a technical approach to exercising the model to reveal its strengths, limitations and assumptions as quickly as possible.

Model critique skills are useful when you’re evaluating someone else’s model. They’re even more important for your own work. As you build a model, you should be subjecting it to regular testing in many ways. Even though testing takes time, it’s actually *much faster* to work this way, because you avoid endless rework cycles.

The model and materials are provided in 2-Analysis-Global.zip.

Other resources:

How to critique a model

Good modeling practices

Writing an SD conference paper

Writing a good system dynamics paper II

Contents

Running Vensim Models with PLE and the Model Reader from Ventana Systems, Inc. on Vimeo.

*Timeline*

0:00 – Introduction, getting the software

1:30 – Running in PLE

10:30 – Limitations & running with the Model Reader

]]>Timeline:

0:00 – Introduction

1:50 – Basic tracing – graphs & trees

5:11 – The table tool

6:44 – Forward tracing

7:30 – Equation editing

8:08 – Tracing with subscripted (array) variables

12:09 – Subscript Control

13:44 – Window cleanup

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Timeline:

0:00 Introduction & background

4:42 Implementation in Vensim using WITH LOOKUP

12:32 Simulating

13:48 (Re)using a separate lookup

17:58 Causal tracing lookups with the Strip Graph tool

]]>Building a Simple Vensim Model from Ventana Systems, Inc. on Vimeo.

Timeline:

- 0:00 – Introduction, new model, adding stocks and flows
- 1:48 – Defining equations
- 5:39 – Running the model & seeing output
- 7:36 – Placing a graph on the screen and running live with Synthesim
- 11:07 – Managing datasets
- 12:29 – Refining the model with auxiliary variables & information arrows
- 15:48 – Defining new equations
- 18:53 – Units check & run
- 20:24 – Causal Tracing
- 22:06 – Conclusion & background