function y = stdnan(x)

% function y = stdnan(x)

%STD	Standard deviation.

%	For vectors, STD(x) returns the standard deviation.

%	For matrices, STD(X) is a row vector containing the

%	standard deviation of each column.

%

%	STD computes the "sample" standard deviation, that

%	is, it is normalized by N-1, where N is the sequence

%	length.

%

%       ignor NaNs

%	See also COV, MEAN, MEDIAN.

%	J.N. Little 4-21-85

%	Revised 5-9-88 JNL

%	Copyright (c) 1984-94 by The MathWorks, Inc.

[m,n] = size(x);

if (m == 1) + (n == 1)

    x = x(isfinite(x));

    m = length(x);

    if m == 0

     y = nan;

    elseif m == 1

     y = 0;

    else 

     y = norm(x-sum(x)/m) / sqrt(m-1);

    end

else

    y = zeros(1,n);

    for i=1:n

        xi=x(:,i);

        xi=xi(isfinite(xi));

        m=length(xi);

        if m == 0

          y(i) =nan;

        elseif m == 1

          y(i) =0;

        else 

          avg = sum(xi)/m;

          y(i) = norm(xi-avg) / sqrt(m-1);

        end

    end

end