** 2-D bilinear data interpolation. **

** ZI = INTERP4(X,Y,Z,XI,YI) uses bilinear interpolation to **

** find ZI, the values of the underlying 2-D function in Z at the points **

** in matrices XI and YI. Matrices X and Y specify the points at which **

** the data Z is given. X and Y can also be vectors specifying the **

** abscissae for the matrix Z as for MESHGRID . In both cases, X **

** and Y must be equally spaced and monotonic. **

** **

** **

** Values of NaN are returned in ZI for values of XI and YI that are **

** outside of the range of X and Y. **

** **

** **

** If XI and YI are vectors, INTERP4 returns vector ZI containing **

** the interpolated values at the corresponding points (XI,YI). **

** **

** **

** ZI = INTERP4(Z,XI,YI) assumes X = 1:N and Y = 1:M, where **

** [M,N] = SIZE (Z). **

** **

** **

** F = INTERP4(Z,NTIMES) returns the matrix Z expanded by interleaving **

** bilinear interpolates between every element, working recursively **

** for NTIMES. INTERP4(Z) is the same as INTERP4(Z,1). **

** **

** **

** See also INTERP5 , INTERP3 . **

** **