Make NaN value part of matrix

I have a 4d velocity matrix in a circular pipe: x,y,z,t

size are as follows:(number of grid points)

x=60,y=60,z=40,t=80

I want to use just 3 planes in x direction and make the remain as a NaN values.

How can I do that?(make just I want to keep 3 planes in x direction.one at the center of pipe,one on top of that and one bottom)

Answer 1

[Ameer Hamza]

Do something like this

x_planes = [1 30 60]; % x-planes to keep
M = % 60x60x60x80 matrix
M_new = M*nan;
M_new(x_planes, :, :, :) = M(x_planes, :, :, :)