How to store values from a loop in a matrix

So I'm still bumbling around MATLAB. Basically I have this for loop taht does what I want but I want it to store the values in a matrix named M3:

    for ii = 1:length(M)
           X = M(ii,2);  
           if X<60
               y = 'F';
           elseif X>=60 & X<70
               y = 'D';
           elseif X>=70 & X<80
               y = 'C';
           elseif X>=80 & X<90
               y = 'B';
           else
               y = 'A';
           end
           GR(ii) = y;
    end
    GR.'

How does one set it to store it in a 1 column, 6 row matrix named M3.

Answer 1

[Andrei Bobrov]

    M3 = cell(size(M,1),1);
    for ii = 1:size(M,1)
           X = M(ii,2);  
           if X<60
               M3{ii} = 'F';
           elseif X>=60 & X<70
               M3{ii}= 'D';
           elseif X>=70 & X<80
               M3{ii} = 'C';
           elseif X>=80 & X<90
               M3{ii} = 'B';
           else
               M3{ii} = 'A';
           end
    end