Running simulink from matlab m file and then getting an output

Suppose I have simulink model called "A"and I run

simOut=sim('A');

from the script. How can I get time series of simulated variables?

Answer 1

[Walter Roberson]

Use set_param() on the appropriate blocks of the model to change the configuration of the model, and then sim() the model and record the results. For example,

gains = [1/10 1 2 5 10 50 100];
ngains = length(gains);
results = cell(ngains,1);
model_name = 'vdp';
block_name = 'vdp/Mu';
for K = 1 : ngains
    set_param(block_name, 'Gain', sprintf('%f', gains(K)));
    results{K} = sim(model_name);
end

[alpedhuez]

Thank you. To be more specific, I try to run

https://www.mathworks.com/matlabcentral/fileexchange/74697-sir-math-model-of-virus-spread-coronavirus-or-other

I did

simOut=sim('SIRcovid2018a');

and the output simOut does not record any variable other than tout. Please advise.

[Walter Roberson]

https://www.mathworks.com/help/simulink/slref/simulink.simulationoutput-class.html#bvom1d1-1

Use the 'SaveState' option.

[alpedhuez]

Thank you. I did

>simOut=sim('SIRcovid2018a','SaveState');

then it says

"The input arguments of a single output sim command should be model name followed by either a structure

with valid parameters as fields with corresponding values or a set of parameter name and parameter

value pairs"

[Walter Roberson]

out1 = sim('SIRcovid2018a', 'SaveState', 'on')

[alpedhuez]

Thank you. This was not clear from the page you mentioned. It would be helpful if that page is edited to be clearer.

The output says index 1, 2, and 3. How can one name these variables when one defines the simulink model?

[Walter Roberson]

That page is an example; the primary source is https://www.mathworks.com/help/simulink/slref/sim.html#namevaluepairarguments

I do not know if there is a way to give individual names to the indices. You could always put in ToWorkspace blocks to save individual signals, or use signal logging. See the hints at https://www.mathworks.com/help/simulink/slref/sim.html#bvfe92n-3

[alpedhuez]

But I assume there is a way to define variables when one set up these blocks in Simulink?

[Walter Roberson]

Signals are not the same as variables in Simulink.

You can name signals

https://www.mathworks.com/help/simulink/ug/signal-basics.html#bs9gzwp

And you can store values persistently by using workspace variables or data store. At the moment, I do not know what the differences are between using workspace variables compared to data store.

https://www.mathworks.com/help/simulink/ug/create-edit-and-manage-workspace-variables.html

https://www.mathworks.com/help/simulink/ug/data-store-basics.html

[alpedhuez]

As an example, I have simulink model

https://www.mathworks.com/matlabcentral/fileexchange/74697-sir-math-model-of-virus-spread-coronavirus-or-other

then I want to understand how I can name the variables of the model so that it can be obtained as variables in Matlab.

[Walter Roberson]

if I recall correctly, that model does not have any variables. That model has states, and it has signals, and it has parameters.

If you are wanting to see final outcomes of signals then ToWorkspace. If you want to see how a signal evolved then log the signal.