MATLAB: Indexing into a cell array to retrieve specific value

Answer 1

You would probably be better off using a table instead of a cell array.

In any case:

sj_name = 'xxxx@gmail.com';
ids = cell2mat(yourcellarray(strcmp(yourcellarray(:, 3), sj_name), 1));

If you are absolutely certain that there is only ever one match:

id = yourcellarray{strcmp(yourcellarray(:, 3), sj_name), 1};