Linear interpolation of a 2d array to another 2d array

Hi,

How can I linearly interpolate a rectangular 2d array (50 by 36) into a another rectagular array say (25 by 18). I know MATLAB's interp1 function can do this but unfortunately it returns "Nan" in some of the output array elements. How can I circumvent this issue ?

[thoughtGarden]

Can you give an example of what you want, say with a 2X2 and 1X2 2d array? interpolation across arrays of different sizes doesn't make much sense (and I'm not sure interp1 can do what you are looking for).

for example:

arr1 = [2,4;5,6];

arr2 = [1,3];

val = yourFunc(arr1,arr2,1.5)

what do you expect val should be?

[Walter Roberson]

imresize() ? Or take the mean or median of each 2 x 2 block perhaps?

Answer 1

[Matt J]

You are getting NaN's because some of the query locations where you have asked interpolation to be performed are outside the boundaries of the array.

However, as the others have said, interpolation is a peculiar way to downsample an array. More typically, you would do 2x2 binning. If that is what you actually want, you could use this FEX file,

https://www.google.com/search?q=sepblockfun&oq=sepblockfun&aqs=chrome..69i57j35i39.2262j0j0&sourceid=chrome&ie=UTF-8

For example

>> A=rand(50,36);

>> B = sepblockfun(A,[2,2],'mean');

>> whos A B
  Name       Size            Bytes  Class     Attributes

  A         50x36            14400  double              
  B         25x18             3600  double