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annotate general/numerical/scalar/lambertw.m @ 61:eff6bddf82e3 tip

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Finally implemented perceptual brightness thing.
author samer
date Sun, 11 Oct 2015 10:20:42 +0100
parents db7f4afd27c5
children
rev   line source
samer@4 1 function W = lambertw(x)
samer@4 2 % lambertw - Lambert's W function
samer@4 3 %
samer@4 4 % lambertw :: real -> real.
samer@4 5 %
samer@4 6 % evaluates W(y) for -1 branch of Lambert W function where
samer@4 7 % y = -exp(-x)
samer@4 8 %
samer@4 9 % The W function satisfies W(t)*exp(W(t)) = t
samer@4 10
samer@4 11 if x<1, error('lambertw: argument must be >= 1'); end
samer@4 12 W=fixpoint(@(w)(-x-log(abs(w))),-x,'its',60);