nansum.m

function y = nansum(x,dim)
%NANSUM Sum, ignoring NaNs.
%   Y = NANSUM(X) returns the sum of X, treating NaNs as missing values.
%   For vector input, Y is the sum of the non-NaN elements in X.  For
%   matrix input, Y is a row vector containing the sum of non-NaN elements
%   in each column.  For N-D arrays, NANSUM operates along the first
%   non-singleton dimension.
%
%   Y = NANSUM(X,DIM) takes the sum along dimension DIM of X.
%
%   See also SUM, NANMEAN, NANVAR, NANSTD, NANMIN, NANMAX, NANMEDIAN.

%   Copyright 1993-2004 The MathWorks, Inc.


% Find NaNs and set them to zero.  Then sum up non-NaNs.  Cols of all NaNs
% will return zero.
if  nargin == 1 & size(x,1) ~= 1
    dim = 1;
elseif nargin == 1 & size(x,1) == 1
    dim = 2;    
end
    
x0 = x;
x(isnan(x)) = 0;

if nargin == 1 % let sum figure out which dimension to work along
    y = sum(x);
else           % work along the explicitly given dimension
    y = sum(x,dim);
end
logic = all(isnan(x0),dim);
y(logic) = NaN;