function value = normal_pdf ( x, mu, sigma )

%% normal_pdf evaluates the normal probabiity density function.
%
%  Input, X(*), evaluation points.
%
%  Input, MU, SIGMA, the mean and standard deviation.
%
%  Output, VALUE(*), the normal PDF evaluated at each value of X.
%
  value = exp ( - ( x - mu ) .^2 / 2.0 / sigma^2 ) ...
    / sqrt ( 2.0 * pi * sigma^2 );

  return
end

