using a function in a for loop

I have a function that interrogates a file and returns a matrix and a boolean. I would like to run this for 12 different parts of a file. The below gives an error that brace indexing is not supported for this variable type. Is there a way to write the below?

for k = 1 : 12
    [CH{k} result{k}] = ytmWdfGetData(fileName, k, 1)
end

Answer 1

[Image Analyst]

Your simplified code works fine. Watch:

fileName = 'snafu.txt';
for k = 1 : 12
    [CH{k} result{k}] = ytmWdfGetData(fileName, k, 1);
end
celldisp(CH)

 
CH{1} =
 
    0.2304

 
 
CH{2} =
 
    0.8215

 
 
CH{3} =
 
    0.3306

 
 
CH{4} =
 
    0.0877

 
 
CH{5} =
 
    0.6618

 
 
CH{6} =
 
    0.8029

 
 
CH{7} =
 
    0.3256

 
 
CH{8} =
 
    0.5995

 
 
CH{9} =
 
    0.5077

 
 
CH{10} =
 
    0.1808

 
 
CH{11} =
 
    0.6645

 
 
CH{12} =
 
    0.1297

 

celldisp(result)

 
result{1} =
 
    0.3809

 
 
result{2} =
 
    0.8788

 
 
result{3} =
 
    0.1505

 
 
result{4} =
 
    0.9295

 
 
result{5} =
 
    0.3460

 
 
result{6} =
 
    0.2646

 
 
result{7} =
 
    0.2070

 
 
result{8} =
 
    0.8174

 
 
result{9} =
 
    0.4201

 
 
result{10} =
 
    0.2801

 
 
result{11} =
 
    0.1869

 
 
result{12} =
 
    0.2093

 

fprintf('Done!\n')

Done!

function [out1, out2] = ytmWdfGetData(arg1, arg2, arg3)
out1 = rand;
out2 = rand;
end

Your error comes from some other part of your code.

Please attach the complete error message -- ALL THE RED TEXT. This includes the line number, the actual line of code that threw the error, and the error description itself.

If you have any more questions, then attach your data and code to read it in with the paperclip icon after you read this:

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[Ted HARDWICKE]

Thanks @Image Analyst. I will add the error message in full next time.

Error message was

Unable to perform assignment because brace indexing is not supported for variables of this type

There are no other parts of my code other than defining the fileName, which works in other functions in this toolbox (wdf access). (I was using 'evaluate selection in command window')

What happened, I assume, is I had CH in workspace from a previous attempt and its type did not support braces. I deleted that from workspace and reran, and it worked as you show above.

Is there a way to get multiple matrices - CH1 matrix, CH2 matrix, etc in the for loop that reads the file/uses the wdf funtion? as opposed to CH() 1x12 cell array with each cell being a 1x10M array? I can work with what I have, and might want to, but will have to modify other parts of my script.

[Image Analyst]

@Ted HARDWICKE no. Well yes, but they're kludgy and not recommended. For example one way is

for k = 1 : 3
    if k == 1
        [CH1, result1] = ytmWdfGetData(fileName, k, 1);
    elseif k == 2
        [CH2, result2] = ytmWdfGetData(fileName, k, 1);
    elseif k == 3
        [CH3, result3] = ytmWdfGetData(fileName, k, 1);
    end
end

Answer 2

[Vilém Frynta]

I would recommend define your variables beforehand with zeros(). This way, you may avoid your brace indexing problem. Then you can asign function results to your variables directly from function (v1) or indirectly (v2).

I'll try to show an example:

v1

% Create zeros beforehand, you will asign function results here
CH = zeros(1:12)        
results = zeros(1:12)

for k = 1 : 12
    [CH(k) result(k)] = ytmWdfGetData(fileName, k, 1)
end

v2 - little diferent version, that I would say is "safer"

% Create zeros beforehand, you will asign function results here
CH = zeros(1:12)        
results = zeros(1:12)

for k = 1 : 12
    [X Y] = ytmWdfGetData(fileName, k, 1)   % Save function results to X and Y
    
    CH(k) = X;                              % Save X and Y to CH and results
    results(k) = Y;
    
end

If you want different variable type (cell, structure), you can change it as you desire; you can use something else than zeros, jsut define your variables and use indexing.

EDIT: Added second version.