Extract values from a matrix by lat lon coordinates

I have a 3 dimensional matrix say X= n*n*data ; where the 3 dimensions represent lat lon and data and X is at 0.5 degree resolution. The I have a another series of lat lon points say

      W=[20 80
       20.2 80.4]

These lat lon points lie within the lat lon limits of X, but do not necessarily coincide with the resolution. I want to find the values of data with respect to the coordinates in W. I tried inpolygon, which rather than giving values for these specific points gives values within the polygon created with the coordinates in W as bound

Answer 1

[KSSV]

Read about interp2

loni = [20 20.2] ;
lati = [80 80.4] ;
zi = interp2(lon,lar,data,loni,lati) ;