How can I rearrange the order of elements in a string given a matrix with positions?

I have a string array of the form: str =["e1","e5", "e7", "e3"] %there are 16 e's in total

I want to take that str and order it such that I get a matrix of the form: M = [ e1 e5 e9 e13; e2 e6 e10 e14; e3 e7 e11 e15; e4 e8 e12 e16]

and then rearrange the matrix with the positions such that I get them ordered like in matrix l.

To do that I wrote:

for i=1:16

    if ismember(sprintf('e%d',i), v)
         Order(i) =  sprintf('e%d',i);
         else
          Order(i)= sprintf('e%d',i);
    end
    [tf,loc] = ismember(sprintf('e%d',i),v);
    Positions(i) = loc;
l = [1 5 2 6;...
     9 13 10 14;...
     3 7 4 8;...
     11 15 12 16];
New_order = Positions(l);

In this example New_order = [1 2 0 0; 0 0 0 0; 4 3 0 0; 0 0 0 0]

Now, the problem is I have another vector b that is the same length as v: b = ( 1 5 7 3); and I want to create a matrix with its elements in the form of New_order, but if I try b(New_order) it won't allow me to do so because New_order contains zeros. How can I rearrange my vector b using New_order such that the output is: [1 5 0 0; 0 0 0 0; 3 7 0 0; 0 0 0 0] ?

Answer 1

[Voss]

v = ["e1","e5","e7","e3"];

% these two lines replace your existing loop:
Order = compose("e%d",1:16);
[~,Positions] = ismember(Order,v);

l = [1 5 2 6;...
     9 13 10 14;...
     3 7 4 8;...
     11 15 12 16];
New_order = Positions(l)

New_order = 4×4

1 2 0 0 0 0 0 0 4 3 0 0 0 0 0 0

% now do the thing with b:
b = [1 5 7 3];

New_b = zeros(size(New_order));
idx = New_order ~= 0;
New_b(idx) = b(New_order(idx))

New_b = 4×4

1 5 0 0 0 0 0 0 3 7 0 0 0 0 0 0