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

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Emerson De Souza
Emerson De Souza 2012-1-16
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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采纳的回答

Image Analyst
Image Analyst 2012-1-16
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.

更多回答（1 个）

Jan
Jan 2012-1-16
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.
  2 个评论
Emerson De Souza
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
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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