Passing one value at a time

Hi,

I need to pass one value at a time from matrix. For example, first value would be 0.0087 the loop execute and display that, then 0.0074 and so on...

Any help is appreciated. Thanks in advance.

Answer 1

[KSSV]

A = rand(5,1) 

A = 5×1

0.0300 0.1842 0.7141 0.0645 0.4457

for i = 1:length(A)
    A(i)
end

ans = 0.0300

ans = 0.1842

ans = 0.7141

ans = 0.0645

ans = 0.4457

[KSSV]

@Sugar Mummy commented: This is still giving dimensionality error because the other parameters (say B,C,D...) are a constant value that's why I need a code that take one constant value at a time.

Your help would be appreciated.

[KSSV]

Show us your code which gave this error.

[Sugar Mummy]

It says..

As told earlier the other parameters have constant values but 'A' parameter need multiple values that should be executed ONE AT A TIME.

[Walter Roberson]

Simulink can receive individual values from MATLAB in at least two different ways:

1. You can use set_param() to change the value of some parameter of some block. For example you could use set_param to change the resistance for an RLC circuit; OR
2. You can change a variable in the workspace of the function being used to invoke sim() to run a model (or sometimes you change the base workspace.)

In the first case where you are using set_param() then the name of the parameter in the block has no connection to the name of the variable in the MATLAB workspace. You could set the parameter name 'blkgain' from the content of the MATLAB variable elephant_toes(K) and Simulink would not have to care that the name of the parameter and the name of the MATLAB variable are different.

In the second case where you are changing workspace values, then you have a potential problem: the workspace variable that is changed must match the variable name used inside the Simulink block (such as in a Math block, or an initialization mask). If your simulink block has A.*B+C and you want to iterate through different A values, then you would need to change the MATLAB variable A .

And that could be a problem if A is also the name of the MATLAB variable that also holds all of the values. You cannot somehow tell Simulink to use the "currently selected" value out of the matrix A and somehow tell MATLAB to "select" a particular location inside A for Simulink to focus on. That will not work.

Instead, you are going to have to rename the aggregate variable that has all of the values, so that it does not match the name used inside Simulink. So for example,

All_A = A;
for K = 1 : numel(All_A)
   %MATLAB workspace variable |A| must be changed to the single value that
   %Simulink is to work with this time
   A = ALL_A(K);
   sim(whatever);
end
A = ALL_A;   %restore after

[Sugar Mummy]

Hi,

Thank you for the response @Walter Roberson. I am not using the variable 'A' it was just for the example.My variable name is 'IR'. Therefore, as per my understanding All_A = IR so what would be 'A' then? Otherwise it would be a undefined variable error.

Btw, I am working on Simulink where I am creating a variable on model workspace, also modifying the code in it to pass each value one at a time while other parameters are constant.

Thanks in advance.

[Walter Roberson]

All_IR = IR;
for K = 1 : numel(All_IR)
   %MATLAB workspace variable |A| must be changed to the single value that
   %Simulink is to work with this time
   IR = ALL_IR(K);
   sim(whatever);
end
IR = ALL_IR;   %restore after

[Sugar Mummy]

@Walter Roberson I tried exactly this way as well but my problem is still giving the same error i-e- dimesionality issue!

As shown in the figure below the All_IR dimension is 5x1

But the IR variable (the main one) value is 1x1 which means that it is taking ONLY the last value of loop.

Could you please guide what could be the reason.

[Walter Roberson]

No computer language can do what you want. The IR variable cannot be simultaneously only a single value (to avoid dimension problems) but also all of the values together.

In terms of the loop I showed before, you would typically record the output of the sim() call, and extract values from that, and store them at the MATLAB level; after the for K loop you would then have the overall results.

[Sugar Mummy]

@Walter Roberson Thank you so much . The sim() command worked for me.

Last thing I want to ask is that Scope is saving only the data of last value of IR and not the overall loop values data. Could you please help me in this.Thanks!

[Walter Roberson]

No, I do not know of any way to get a Simulink Scope block to save values from previous runs.

I recommend saving the outputs at the MATLAB level and plotting them at the MATLAB level.

All_IR = IR;
for K = 1 : numel(All_IR)
   %MATLAB workspace variable |A| must be changed to the single value that
   %Simulink is to work with this time
   IR = ALL_IR(K);
   simOut = sim(whatever);
   output_wanted{K} = find(simOut, 'VariableYouWantTheValueOf');
end
IR = ALL_IR;   %restore after
outputs_as_matrix = cell2mat(cellfun(@(C) C(:), output_wanted, 'uniform', 0));
plot(ALL_IR, outputs_as_matrix)

except that you might need to record another axis of values and use plot3()

[Sugar Mummy]

@Walter Roberson Thank you Sir!

[Sugar Mummy]

@Walter Roberson

The command

output_wanted{K} = find(simOut, 'VariableYouWantTheValueOf');

is not working for me as I have multiple(12) variables attached to the scope.

Can you please help anything relatedly so I can store the whole Scope data in Simulink. Thanks!

[Walter Roberson]

Store the names of the variables in an array, and use a loop to call find(simOut, NAME) for each of the variables.

[Sugar Mummy]

Thank you for the help!