This tutorial demonstrates how to create a stock-and-flow diagram simulation in Vensim, including setting model parameters, defining stocks and flows, and generating simulation results and plots. Key moments: 00:00 Understanding how to utilize stock and flow diagrams in Vensim is crucial for creating dynamic system simulations. Setting model parameters like initial time, final time, and time step are essential for accurate numerical integration. -Customizing model settings such as time parameters and units in Vensim ensures accurate simulation results. Exploring advanced options in Vensim allows for more complex modeling capabilities. -Adjusting font sizes, creating stocks, and defining flows are fundamental steps in building a Vensim model for dynamic system simulations. Understanding the workflow of setting up levels and rates is key to model construction. 04:03 Creating a stock and flow diagram involves naming and connecting stocks, flows, and auxiliary variables with arrows to show causal links for system dynamics analysis. -Naming and double-clicking on stocks and flows to create connections in the diagram is crucial for clarity and accuracy in system dynamics modeling. -Adding auxiliary variables like average time until reproduction and average lifetime enhances the complexity and accuracy of the system dynamics model. -Utilizing arrows to connect variables in the diagram visually represents causal links and aids in understanding the relationships between different components. 08:06 Annotations can be added to stock and flow diagrams to enhance readability, emphasizing causal links and feedback loops. Equations need to be resolved by inputting parameters and formulas to simulate the diagram accurately. -Adding annotations enhances the clarity of causal links and feedback loops in stock and flow diagrams, improving understanding for readers. -Resolving equations in diagrams involves inputting parameters and formulas accurately to ensure proper simulation and functionality. 12:10 It is crucial to regularly save your work in simulation software like Vensim to prevent data loss and enable automated backups, especially in case of frequent crashes, ensuring the initial conditions for stocks are set correctly. -Importance of setting initial conditions for stocks to ensure accurate simulation results and enable proper functioning of the software's numerical integration capabilities. -Utilizing simulation software features like saving simulations under specific file names corresponding to parameters used, enabling easy identification and management of multiple datasets. 16:15 The video demonstrates how to manipulate and visualize simulation data in a software tool. It shows how to plot different variables and customize the appearance of the graphs. -The video explains how to save and manipulate simulation files with different parameters and names, allowing for multiple variations of the data to be generated. -It demonstrates how to plot and analyze simulation outputs, including stocks, flows, and variables, providing insights into the simulated system's behavior. -The tutorial showcases how to customize graph appearance by adjusting options such as legends, colors, line patterns, and other visual elements to enhance data visualization. 20:21 Adding units to graphs in Vincent allows for clear visualization of data. Tables in Vincent enable users to extract raw data for further analysis and can be saved as text files for easy access. -Adding units to graphs in Vincent improves data interpretation and presentation, enhancing overall clarity in visualizations. -Using tables in Vincent provides a convenient way to extract raw data for analysis and export them as text files for easy sharing and further processing. 24:24 It is important to understand how to format and manipulate data axes in Excel for better control over data presentation and analysis. Differentiating between table time down and table formats can help in organizing data conveniently. -Exploring different data presentation formats like rows and columns in Excel for increased control over data visualization and manipulation. -Demonstrating how to adjust parameters without losing old data by saving files with new parameters and comparing datasets for analysis in Excel. -Managing and organizing datasets by loading, unloading, and deleting specific data sets in Excel for clearer and more focused data analysis.
Hello, what should I do if I wanted a variable to change value at a specific time. I want my variable = 1 but change and become 2 when time = 100 days. In other words, how do I use time as a variable in an equation of another variable?
There are a number of ways to accomplish this in Vensim. The simplest is to use the STEP built in function, which is zero up until a specified time and then jumps to a specified value at that time. You can add it to an initial condition to get the behavior you want. See the example in the Vensim documentation at the link below, which describes exactly the case you want and shows you how to use STEP to do it. There are a number of other time functions that you can use for similar tasks. You can also use a lookup table with time as an input. www.vensim.com/documentation/20770.html
Which equation? I use a basic population growth model in this tutorial just as an example. The flow expressions are the instantaneous rates of change over time. Thus, the death outflow is the number of bacteria divided by the average lifetime -- at that instant, the population is declining at that rate.
@@quinnikeaisy55 These are parameters that would have to be determined by consulting a reference on the particular bacteria being modeled. For my example, I just picked them arbitrarily. For a real modeling case, I would have to determine the average lifetime of a bacterium and the average time for a bacterium to asexually reproduce -- these would be things I could ask a micriobiologist (or consult a reference text) who had measured them in real bacteria.
![Stocks and Flows [The Climate Leader]](http://i.ytimg.com/vi/nRlYGDBGcRA/mqdefault.jpg)
Thank you. I'm finding Vensim to be extremely unintuitive, but this helped me understand some of its logic.
Excellent tutorial for beginners! I feel a lot more relaxed about Vensim now.
Thank you so much! amazing way of explanation! made me understand as I am a beginner to the system dynamics
Thank you so much Ted, this was a very helpful introduction!
This tutorial demonstrates how to create a stock-and-flow diagram simulation in Vensim, including setting model parameters, defining stocks and flows, and generating simulation results and plots.
Key moments:
00:00 Understanding how to utilize stock and flow diagrams in Vensim is crucial for creating dynamic system simulations. Setting model parameters like initial time, final time, and time step are essential for accurate numerical integration.
-Customizing model settings such as time parameters and units in Vensim ensures accurate simulation results. Exploring advanced options in Vensim allows for more complex modeling capabilities.
-Adjusting font sizes, creating stocks, and defining flows are fundamental steps in building a Vensim model for dynamic system simulations. Understanding the workflow of setting up levels and rates is key to model construction.
04:03 Creating a stock and flow diagram involves naming and connecting stocks, flows, and auxiliary variables with arrows to show causal links for system dynamics analysis.
-Naming and double-clicking on stocks and flows to create connections in the diagram is crucial for clarity and accuracy in system dynamics modeling.
-Adding auxiliary variables like average time until reproduction and average lifetime enhances the complexity and accuracy of the system dynamics model.
-Utilizing arrows to connect variables in the diagram visually represents causal links and aids in understanding the relationships between different components.
08:06 Annotations can be added to stock and flow diagrams to enhance readability, emphasizing causal links and feedback loops. Equations need to be resolved by inputting parameters and formulas to simulate the diagram accurately.
-Adding annotations enhances the clarity of causal links and feedback loops in stock and flow diagrams, improving understanding for readers.
-Resolving equations in diagrams involves inputting parameters and formulas accurately to ensure proper simulation and functionality.
12:10 It is crucial to regularly save your work in simulation software like Vensim to prevent data loss and enable automated backups, especially in case of frequent crashes, ensuring the initial conditions for stocks are set correctly.
-Importance of setting initial conditions for stocks to ensure accurate simulation results and enable proper functioning of the software's numerical integration capabilities.
-Utilizing simulation software features like saving simulations under specific file names corresponding to parameters used, enabling easy identification and management of multiple datasets.
16:15 The video demonstrates how to manipulate and visualize simulation data in a software tool. It shows how to plot different variables and customize the appearance of the graphs.
-The video explains how to save and manipulate simulation files with different parameters and names, allowing for multiple variations of the data to be generated.
-It demonstrates how to plot and analyze simulation outputs, including stocks, flows, and variables, providing insights into the simulated system's behavior.
-The tutorial showcases how to customize graph appearance by adjusting options such as legends, colors, line patterns, and other visual elements to enhance data visualization.
20:21 Adding units to graphs in Vincent allows for clear visualization of data. Tables in Vincent enable users to extract raw data for further analysis and can be saved as text files for easy access.
-Adding units to graphs in Vincent improves data interpretation and presentation, enhancing overall clarity in visualizations.
-Using tables in Vincent provides a convenient way to extract raw data for analysis and export them as text files for easy sharing and further processing.
24:24 It is important to understand how to format and manipulate data axes in Excel for better control over data presentation and analysis. Differentiating between table time down and table formats can help in organizing data conveniently.
-Exploring different data presentation formats like rows and columns in Excel for increased control over data visualization and manipulation.
-Demonstrating how to adjust parameters without losing old data by saving files with new parameters and comparing datasets for analysis in Excel.
-Managing and organizing datasets by loading, unloading, and deleting specific data sets in Excel for clearer and more focused data analysis.
Thank you for your time
i will look forward to any video you post
Thank you. Very helpful video.
Hello, what should I do if I wanted a variable to change value at a specific time. I want my variable = 1 but change and become 2 when time = 100 days. In other words, how do I use time as a variable in an equation of another variable?
There are a number of ways to accomplish this in Vensim. The simplest is to use the STEP built in function, which is zero up until a specified time and then jumps to a specified value at that time. You can add it to an initial condition to get the behavior you want.
See the example in the Vensim documentation at the link below, which describes exactly the case you want and shows you how to use STEP to do it. There are a number of other time functions that you can use for similar tasks. You can also use a lookup table with time as an input.
www.vensim.com/documentation/20770.html
How we determine the equation?
Which equation? I use a basic population growth model in this tutorial just as an example. The flow expressions are the instantaneous rates of change over time. Thus, the death outflow is the number of bacteria divided by the average lifetime -- at that instant, the population is declining at that rate.
@@TedPavlic how did u know that average time is 0.75 and 3?
@@quinnikeaisy55 These are parameters that would have to be determined by consulting a reference on the particular bacteria being modeled. For my example, I just picked them arbitrarily. For a real modeling case, I would have to determine the average lifetime of a bacterium and the average time for a bacterium to asexually reproduce -- these would be things I could ask a micriobiologist (or consult a reference text) who had measured them in real bacteria.
💙