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annotate general/numerical/lambertw.m @ 4:e44f49929e56

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Adding reorganised general toolbox, now in several subdirectories.
author samer
date Sat, 12 Jan 2013 19:21:22 +0000
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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);