"...with the name for the structures being rate100,rate150,rate200,..... So far my for loop has two issues."
The main issue is that you are forcing meta-data into variable names.
Forcing meta-data into variable names is usually a sign that you are doing something wrong:
If you simply stored that meta-data inside the structure and used exactly the same variable names in every MAT file, then your code would be simpler, more efficient, and much more robust:
saveDir = 'my/path/name';
for k = ..
S.minTime = tmin;
S.maxTime = tmax;
S.rate = whatever_meta_data_you_want;
% Save structure
F = [saveDir,'/rate',num2str(cnt),'.mat'];
save(F, 'S'); % simpler and much more robust
end
In contrast, your approach of forcing meta-data into the variable names suffers from a number of problems:
(that explanation is for fieldnames, but it applies just as much to forcing meta-data into variable names)
