view general/numerical/scalar/erfp.m @ 61:eff6bddf82e3 tip

Finally implemented perceptual brightness thing.

function y=erfp(x)
% erfp - returns Pr(X>x) for a normalised Gaussian random variable
%
% erfp :: X:real -> Z:real.
%
% Y = integeral from X to infinity of 
% (1/sqrt(2*pi)) * exp(-0.5*t.^2)

y = erfc(x/sqrt(2))/2;