How to save the elements of an array one at a time in a .mat file?

Consider the following loop:

for i=1:100
 X(i) = 2*i;
end

I would like to save the values of X, one iteration at a time, as and when it is generated, in a .mat file. This is the code I tried:

fopen('test.mat','a+');
for i=1:100
 X(i) = 2*i;
 save('test.mat','X(i)','-append')
end

This is the output I got 'X(i) is not a valid variable name'. When I try

save('test.mat','X','-append')

instead, I get the error 'Unable to write to MAT-file. File may be corrupted'. Is there a solution?

[per isakson]

See matfile, Access and change variables directly in MAT-files, without loading into memory

Answer 1

[Abhishek GS]

Hi Sundar,

Assuming you need a representation of the variable and the iteration number in the .MAT file, you could try something like this.

for i=1:100
  X(i) = 2*i;
  varname=sprintf('X_%d',i);
  assignin('caller',varname,2*i);
     if (exist('test.mat'))
         save('test.mat',varname,'-append')
     else
         save('test.mat',varname)
     end
end

Hope this helps,

Abhishek