Documentation of nmedian

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Function Synopsis

y = median(x,dim)

Help text

NMEDIAN Median value, ignoring NaN.
   Same as MEDIAN, but NaN's are ignored.

 uses :	intvers.m

Listing of function nmedian

function y = median(x,dim)

%   Copyright (c) 1997 by Toby Driscoll.
%   Adapted from MEDIAN.M, written by The MathWorks, Inc.
%   added backward compatibility	G.Krahmann, LODYC Paris

if nargin==1, 
  dim = min(find(size(x)~=1)); 
  if isempty(dim), dim = 1; end
end
if isempty(x), y = []; return, end


if intvers>4
  siz = [size(x) ones(1,dim-ndims(x))];
  n = size(x,dim);

% Permute and reshape so that DIM becomes the row dimension of a 2-D array
  perm = [dim:max(length(size(x)),dim) 1:dim-1];
  x = reshape(permute(x,perm),n,prod(siz)/n);

% Sort along first dimension
  x = sort(x,1);

  n = sum(~isnan(x));
  y = zeros(1,size(x,2));
  for j = 1:size(x,2)
     if n(j)==0
        y(j) = NaN;
     elseif rem(n(j),2) % Odd number of elements along DIM
        y(j) = x((n(j)+1)/2,j);
     else % Even number of elements along DIM
        y(j) = (x(n(j)/2,j) + x((n(j)/2)+1,j))/2;
     end
  end
  
% Permute and reshape back
  siz(dim) = 1;
  y = ipermute(reshape(y,siz(perm)),perm);

else

  [m,n] = size(x);
  y = NaN*ones(1,n);
  for j =1:n
    i = find(~isnan(x(:,j)));
    if ~isempty(i)
      y(j) = median(x(i,j));
    end
  end

end