How can I used 'save()' command in matlab function block?

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SyukriY 2016-12-9

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https://ww2.mathworks.cn/matlabcentral/answers/316137-how-can-i-used-save-command-in-matlab-function-block

评论： Kerry Schutz 2020-11-13

Hi, everyone. I really need everyone help. I can't used 'save()' command in matlab function block. Do anyone know? and how can I change the 'save()' command in the matlab function block?

function [DayOfOvule,Dmax,CycleLength]  = detection(dataB,dataA,limit,CL)
%#codegen
A = dataA; 
B = dataB;
fileD = 'difference.txt';
if (A > limit) && (B < limit)
  D = A - B;    
  save(fileD, 'D');
elseif (A > limit) && (B > limit)
  %startCountDown     
else    
end
  CycleLength = CL;
  S = load(fileD, 'D');
  Dmax = max(S.D);
  DayOfOvule = 13; 
end
end

Does matlab can hold a value? For example, I have my data in timeseries and I want to calculate the differences between each data. Then, from differences I want to find the largest value of the different.

#credit to Walter Roberson for teach me something about delay.

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SyukriY 2016-12-9

编辑：SyukriY 2016-12-9

在 MATLAB Online 中打开

I'm just curious...

What is the protocol code to use commands in the MATLAB function block? because until this minute I try to use different ways of 'saving or hold' the data like saving or holding the data in EEPROM.

For example:

if I'm used 'table' command

The 'table' class does not support code generation.
Function 'MATLAB Function Differentiation' (#38.235.243), line 11, column 9:
"table(D)"
Launch diagnostic report.

If I'm used 'writetable' command

 The function 'writetable' is not supported for standalone code generation. See the documentation for coder.extrinsic to learn how you can use this function in simulation.
Function 'MATLAB Function Differentiation' (#38.250.312), line 12, column 5:
"writetable(D,'myData.csv','Delimiter',',','QuoteStrings',true)"
Launch diagnostic report.

If I'm used 'csvread' command

The function 'csvread' is not supported for standalone code generation. See the documentation for coder.extrinsic to learn how you can use this function in simulation.
Function 'MATLAB Function Differentiation' (#38.475.498), line 18, column 5:
"csvread('myData.csv',D)"
Launch diagnostic report.

If I'm used 'save' command

Function 'save' is not supported for code generation and the coder.extrinsic directive cannot be applied to 'save'. Rewrite your code so it does not use 'save'.

Does anyone know why?

SyukriY 2016-12-9

编辑：SyukriY 2016-12-9

Note that,

I'm using MATLAB function block to code a function in simulink.

Kerry Schutz 2020-11-13

You'll need to use a file I/O function that is supported for code generation. Two examples of that would be fwrite, for binary files, and fprintf, for text files.

https://www.mathworks.com/help/releases/R2020b/matlab/ref/fwrite.html

https://www.mathworks.com/help/releases/R2020b/matlab/ref/fprintf.html

These functions, while they work, are still not as convenient as using save due to the overhead associated with the particulars of using lower-level file I/O functions.

You might consider a different approach to saving data in your Simulink model that originates inside a MATLAB Function block. You can try outputting the data back onto a Simulink output port and then using the To File block to save the data to a .mat file. That might be cleaner in the end.

And yes, I realize this is almost 4 years after you submitted your question but I hope it helps someone out there.

Kerry