Get the first row in Matlab for multiple steps

Question

I have a y in the following format (printed):

y(:,:,1) =

     1     0     0
     0     1     0
     0     0     1


y(:,:,2) =

    0.9263    0.3468    0.1474
   -0.3468    0.6314    0.6936
    0.1474   -0.6936    0.7052


y(:,:,3) =

    0.7595    0.4380    0.4811
   -0.4380   -0.2027    0.8760
    0.4811   -0.8760    0.0378

[...]

y(:,:,19) =

    0.6071   -0.1174    0.7859
    0.1174   -0.9646   -0.2349
    0.7859    0.2349   -0.5717


y(:,:,20) =

    0.7189   -0.4086    0.5622
    0.4086   -0.4055   -0.8172
    0.5622    0.8172   -0.1244

How can I convert it to:

y(:,:,1) =

     1     0     0


y(:,:,2) =

    0.9263    0.3468    0.1474


y(:,:,3) =

    0.7595    0.4380    0.4811

[...]

y(:,:,19) =

    0.6071   -0.1174    0.7859


y(:,:,20) =

    0.7189   -0.4086    0.5622

(To get the first, second and third row for each 20 steps and store it in another variable.)

Answer 1

If you mean "how to get the first row", you can do it like this:

other_matrix = y(1,:,:)

Answer 2

As @blackbird said,

Access your matrix as y(1,:,1),y(1,:,2)......y(1,:,19),y(1,:,20)

Answer 3

The documentation explains how to use the colon operator (:) to get the first row.