How to update a value in different raw after performing validity check at one raw?

I have a file containing 5 raws including the titles and 3 columns. After performing a validity check for value at raw(2,2), I will need to update the raw(2,3) with another value. However, I failed to do so. Please advise.

[Massimo Zanetti]

Please, upload an example of you matrix

[Guillaume]

I assume by raw you mean row? Otherwise, I have no idea what you're talking about.

We have no idea how you're reading the file nor what is in it. Files don't have titles or columns as such, so please show us the code that is not working, or an example file.

[KenL]

file={'No','Question','Length';'1','how are you?','';'2','What is your name?','';'3','Where do you stay?','';'4','How old are you?',''}

I want to figure out the length for all the text columns.

[KenL]

Pls advise.

Answer 1

[Guillaume]

If I understood correctly

file = {'No','Question','Length';'1','how are you?','';'2','What is your name?','';'3','Where do you stay?','';'4','How old are you?',''};

file(2:end, 3) = cellstr(num2str(cellfun(@numel, file(2:end, 2)))

will work. Or if you have R2016b:

file = {'No','Question','Length';'1','how are you?','';'2','What is your name?','';'3','Where do you stay?','';'4','How old are you?',''};

file = string(file);
file(2:end, 3) = file(2:end, 2).strlength;

Answer 2

[Andrei Bobrov]

 file(2:end,3) = cellfun(@(x)sprintf('%d',numel(x)),file(2:end,2),'un',0)