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

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

[Stephen23]

Rather than using evil EVAL, it is simpler, more efficient, and much more robust to use dynamic fieldnames:

https://www.mathworks.com/help/matlab/matlab_prog/generate-field-names-from-variables.html

test = struct();
for k = 1:100
    fld = sprintf('p%d',k);
    test.(fld) = 1:1:2e5;
end
save('test.mat','-v7.3','-struct','test');

Answer 1

[Stephen]

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.

[Yu Li]

Thank you.

Answer 2

[埃博拉酱]

save(filename,'-fromStruct',test);