How can I obtain new coordinates of elements in strings array?

I have an input like: A = ["e2_u3", "e4_u1", "e3_u2", "e_3_u1", "e2_u2", "e1_u1"]

and I want to create: M(i,j) = ["e1_u1" "e1_u2" "e1_u3"... "e1_uj" ;...;"ei_u1"..."ei_uj"].

In the case that the element exists in A, I want it to appear in M, and then I want to be able to say what was it's position in A.

Example:

txt= ["e2_u3", "e4_u1", "e3_u2", "e_3_u1", "e2_u2", "e1_u1"];

e = 4; u = 4;

order = strings(e,u);

for i=1:e

    for m=1:u
        if ismember(sprintf('e%d_u%d',i,m),txt)
            order(i,m) = sprintf('e%d_u%d', i,m);
        else
            order(i,m)= 'Nan';
        end
    end
end

Now, I don't know how to tell the coordinate change from 'txt' to 'order'.

Answer 1

[Matt J]

Call ismember with two outputs

[tf,loc]=ismember(sprintf('e%d_u%d',i,m),txt(:))

The output "loc" gives the location within txt(:).