How to make a variable in one .m file make changes in another .m file?

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Emerson De Souza 2012-1-16

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Hi, I change the variable of one .m file and want that this number be automatically rewritten for another variable in another .m file.

For example, I open the file:

open cpcorr.m;

and change the value in line 76 as below:

CORRSIZE = 4;

Now I have a new newfile.m with the variable

CS=CORRSIZE;

Thus, when I change the value of CORRSIZE in cpcorr.m, I wish also that the value of CS in file1.m be automatically changed, for this particular example, CS would equal 4.

I hope someone knows how to fix this.

Thanks in advance for your help

Emerson

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Robert Cumming 2012-1-16

how do the 2 functions interact - does one call the other?

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Answer 1

Image Analyst 2012-1-16

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You can't do it if all you do is to change the text in the m-file. After all, an m-file is stored simply as a flat text file on disk. One text file sitting there on disk is not going to know that it needs to change itself if some other file somewhere on disk changed itself. However if you run the m-file, then you can put code in it to change the variable value in the other m-file. Look at the assignin() function.

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Answer 2

Jan 2012-1-16

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在 MATLAB Online 中打开

There is way to let M-files interact magically.

If you want to share the definition of a variable, create a dedicated function for defining the values:

function Value = ShareData(Name)
switch Name
  case 'CORRSIZE'
    Value = 4;
  case 'AnotherVariable'
    Value = 1:17;
  otherwise
    error(['Tools:', mfilename, ':UnknownName'], ...
          'Unknown name: %s', Name);
end

Now all functions, which need the same value for a specific variable can use:

CS = ShareData('CORRSIZE');

This is a programmatical way to create "global" data. Another method would be to use the global statement of Matlab. But this is less secure, because then the value can be modified from anywhere, while the ShareData-function approach ensures, that there is only one location, where the values are defined.

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Emerson De Souza 2012-1-16

Hi Simon, thanks for trying to help. I followed your suggestions and wrote as follow:

function Value = ShareData(cpcorr.m)

switch cpcorr.m

case 'CORRSIZE'

Value = 4;

case 'AnotherVariable'

Value = 1:17;

otherwise

error(['Tools:', mfilename, ':UnknownName'], ...

'Unknown name: %s', Name);

end

CS = ShareData('CORRSIZE');

but unfortunately I obtain the error message:

??? Error: File: MYFILE.m Line: 1 Column: 34

Unexpected MATLAB operator.

How should I use your suggestion correctly?

In the file cpcorr.m I write the value of the variable CORRSIZE.

Then there will be multiple files.m with arbitrary new variables such as CS, VAR1, VAR2, ETC which will have the same value as CORRSIZE.

I don't know yet how to share this value.

Thanks in advance for your help

Emerson

Walter Roberson 2012-1-16

cpcorr.m is not a valid variable name that can appear as the name of a dummy argument to a function(). In the dummy argument to a function, variable names must be simple names with no '.' and no indexing .

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