save problem: -STRUCT must be the name of a scalar structure variable

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Yu Li
Yu Li on 14 Sep 2018
Commented: Stephen on 23 Jul 2021
I generated a struct file and tried to save it, but Matlab occurs error: The argument to -STRUCT must be the name of a scalar structure variable.
Below are the test code:
for i=1:1:100
fprintf('%0dth data.\n',i)
eval(['test.p',num2str(i),'=1:1:2e5;'])
end
save('test.mat','-v7.3','-struct','S');
is there any problem with my code?
Thanks!
Yu
  1 Comment
Stephen
Stephen on 23 Jul 2021
Rather than using evil EVAL, it is simpler, more efficient, and much more robust to use dynamic fieldnames:
test = struct();
for k = 1:100
fld = sprintf('p%d',k);
test.(fld) = 1:1:2e5;
end
save('test.mat','-v7.3','-struct','test');

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Accepted Answer

Stephen
Stephen on 14 Sep 2018
It is unclear from your post what the data type of variable "S" is. But the error is telling you that "S" is NOT a structure. You can either:
1) Change "S" to a structure variable containing the data you want to save.
or
2) Remove the '-struct' argument from the save command.

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