As you've done it there is no need to wrap the string sheets{i} into a cell array. The problem you have comes from that and not from makeValidName. Since you pass a cell array, you get a cell array back from makeValidName. You can't use a cell array as a field value, so you would have to extract your modified sheet name from the cell array. So one way to fix it would be:
for i = 1:n
[~, data_text, data_raw] = xlsread(doc_name, sheets{i}) % Read sheet to Matlab
N = matlab.lang.makeValidName(sheets{i}, 'ReplacementStyle', 'delete');
sheet_struct.(N) = data_raw;
end
The other option is to simply call makeValidName outside of the loop at once for all the sheet. That should be faster as well:
N = matlab.lang.makeValidName(sheets, 'ReplacementStyle', 'delete');
for i = 1:n
[~, data_text, data_raw] = xlsread(doc_name, sheets{i}) % Read sheet to Matlab
sheet_struct.(N{i}) = data_raw;
end
Personally, I think that dynamic field names are just as bad an idea as dynamic variables, but that's another topic entirely.
