Ventana software support forum

hi,

i am having a problem in making sensitivity simulations. what i do was: i click the button of start sensitivity simulation. then, i select one of my controller variable (lets says percentage of forest areas). i make intuitive value for minimum and maximum. then when i click finish button, the model seems right doing the sensitivity. it runs 200 times of simulation. the problem is when i look through sensitivity graphs, i can not see any changes. the only changes is there is a legend of percentage (which i suspect of percentile). you can see from the uploaded graphs. in my opinion, when we change the percentage of forest areas, the water discharge variables will change a lot. but, the graph do not show any changes.

any suggestions?

thanks,
adjie

We cannot really offer any advice unless we can see the model and see what you are doing.

Do these values change if you run in SynthEsim mode and change the value for "percentage of forest areas"?

thanks for your prompt response. i attach the simple version of my model in doing sensitivity analysis. may be i ask the basic line of doing the sensitivity analysis in vensim. what do i need to do in making sensitivity simulation on vensim? at this stage, i take a case as on attachment. for example: i put a = 10, b is equal to a*100 and c is equal to b/100. when i do sensitivity simulation with the minimum of a is 1 and the maximum of 100. i can see the shaded areas based on percentile in variable a when i click the sensitivity graph. but, i don't see the shaded areas in variable b and c. when i look through the example of sensitivity analysis, they are all shaded. would you mind explaining about this issue, please?

Haven't had a chance to look at your model, but one general caveat: sensitivity graphs will only show changes for variables that are included in your savelist, and for the first loaded dataset, so be sure that you're looking at the right things.

Tom

Hi,
Just to continue with the sensitivity theme, I tested some parameters and see the results on my variables in the graphs, I saved values just for my interest variables in a lst. I would like to observe the values resulting form the different parameters but I don't know how to open this list. Can you give me a light?
Thanks

Do you mean to open the save list you created? If yes, open it in notepad, it is just a plain text file.

Excuse me, I think I expressed bad my need.
I would like to have the result in number of my key variables at the end of the simulations with the values of the parameters. I mean, if I test the sensibility of a parameter a between 0.1 and 0.2, with a random uniform distribution, I would like to have the values of my key variable for each of the parameter between 0.1 and 0.2. When I open in a notepad the lst. I just see the name of the variables chosen without numbers to evaluate numerically the differences between the simulations.
Thanks

Use Model>Export Dataset... to export your sensitivity run to a tab-delimited file, then you can explore the results (including the input distribution) as needed. Often you'll want to check the option to export only Final Time results.

Excellent ! thanks