function [f_std] = nanstd(data);
%
%   [f_std] = nanstd(data);
%
%Function which calculates the std (not NaN) of data containing
%NaN's.  NaN's are excluded completely from calculation.

[m,n] = size(data);

for index = 1:n;
    not_nans = find(isnan(data(:,index)) == 0);
        if length(not_nans) > 0;
            f_std(index) = std(data(not_nans,index));
        else
            f_std(index) = NaN;
        end
end