One sys multiple validation

Hello,

I'm trying to use the compare function to compare one sysid and three validation data. But Matlab always uses z_1 for validation. Why?

Another solution could be to plot sys, z_1,z_2, and z_3 in the same window, but I need to figure out how to do this because sys is an idpoly (structure) variable.

compare(sys,z_1,z_2,z_3)

Answer 1

[Tianyu]

Hi isabel,

https://www.mathworks.com/help/ident/ref/compare.html

compare always uses one dataset for validation. It is used to compare the performance of different models with respect to the same validation set.

compare(data, sys1, sys2, sys3)

If you want to check the performance for different data sets:

compare(z1, sys)

compare(z2, sys)

compare(z3, sys)

If you want to plot all data in one figure, you can simulate the trajectory first:

y = sim(sys,data);

plot(y.OutputData)

hold on

plot(z1.OutputData)

plot(z2.OutputData)

plot(z3.OutputData)

[isabel]

Hi Tianyu, Thank you!!

I want to simulate different datasets z1, z2, and z3, like the first example, but show them in the same plot. Can I do this with the compare function? Or only like the second example?

[Tianyu]

compare function cannot be directly used for your purpose.

You need to customize your plot using the last workflow I provided.

To get fit information:

[~,fit] = compare(z1,sys)

Then you can plot all validation sets and add information using legend function.

https://www.mathworks.com/help/matlab/ref/legend.html

[isabel]

Thank you! That was very helpful!