transform vector in 2 dimensions into one in 3

for i = 1:duration
    traci.simulation.step();
 
   for n = 1: length(inductionID)           
            veicoliOGNIISTANTEsuInduction(n,i)=traci.inductionloop.getLastStepVehicleNumber(inductionID{n});       
    end
    for v=1:length(k)
      
      if i==t(v)
        
        for n = 1: length(inductionID)
            veicoliT(n,v)=sum(veicoliOGNIISTANTEsuInduction(n,(t(v)-(T-1)):t(v)));
        end
        newgreentime(:,v)=L*veicoliT(:,v); % L is a constant matrix
      end
   end

hi all, i have a vector n rows by v (whose columns are indexed). my vector newgreentime (:, v) in the considered v becomes a vector 4 x1, I would like to use this vector in a 3 dimensional vector 2x2xv how can I do it?

Answer 1

[Walter Roberson]

newgreentime(:,:,v) = reshape(L*veicoliT(:,v), 2, 2); % L is a constant matrix

This assumes that you want the order

A B C D ->
[A C
 B D]

if you need

[A B
 C D]

then

newgreentime(:,:,v) = reshape(L*veicoliT(:,v), 2, 2).'; % L is a constant matrix

[Marco Carapellese]

thank you very much for the answer. A curiosity why to "reshape (L * vehiclesT (:, v), 2, 2). '" Why is there also that point near the closing parenthesis? it seems to work for what I want, however as soon as I can fully verify, thanks again

[Walter Roberson]

You have a vector of 4 elements. Compare

v = [1;2;3;4]

v = 4×1

1 2 3 4

reshape(v,2,2)

ans = 2×2

1 3 2 4

reshape(v,2,2).'

ans = 2×2

1 2 3 4

If you want adjacent elements in the vector to form columns, then do not use the .' but if you want adjacent elements in the vector to form rows, then you need the .' operator.

The .' operator is formally known as transpose:

transpose(reshape(v,2,2))

ans = 2×2

1 2 3 4

In general, if you have a vector v and you want to form an A by B matrix out of it, your choices are

reshape(v, A, B)   %go down the columns
reshape(v, B, A).' %go across the rows

[Marco Carapellese]

thank you so much. Because i have see that it works also with " ' " as well as " .' "

[Voss]

" .' " (dot single-quote) is transpose.

" ' " (single-quote) is complex conjugate transpose.

If the thing you are transposing (say X) contains only real values (i.e., no complex numbers), then X.' is the same as X'