hypsom_median

 PURPOSE: colfilt function to calculate the mean of the highest 25%
 altitude values. Returns NaN if more than 50% of input cells are NaN,
 else removes NaN cells for calculation.

 See also: colfilt()

 Felix Hebeler, Geography Dept., University Zurich, Jan 2007.

0001 function [r] = hypsom_median(X)
0002 % PURPOSE: colfilt function to calculate the mean of the highest 25%
0003 % altitude values. Returns NaN if more than 50% of input cells are NaN,
0004 % else removes NaN cells for calculation.
0005 %
0006 % See also: colfilt()
0007 %
0008 % Felix Hebeler, Geography Dept., University Zurich, Jan 2007.
0009 
0010 n=sum(isnan(X(:)));
0011 if n>0
0012     if n>=numel(X)/2
0013         r=nan;
0014         return
0015     else
0016         X(isnan(X))=[];
0017     end
0018 end
0019 r=median(X(:));