changing a 3d matrix to a 2d matrix

Hi,

I have a 3 dimensional array, dimensions x,y,z=219x289x43.
This is an array of temp data on a grid where x and y indicate a grid point on a latitude, longitiude grid and z is height. I have selected a number of grid points from this matrix and I now want to remove all the others so that I have for example an array 10x43.

Any help on how to do this would be appreciated?