HalfMax.m

function FWHM = HalfMax(sigma);
% HALFMAX Full width half maximum of a Gaussian filter.
%	HalfMax returns FWHM, the full width half maximum of
%	a Gaussian filter of standard deviation equals to sigma pixels.
%		E.g., FWHM = HalfMax(20);
% 
% See also DEMOSTAT4CI
% 
% The Stat4Ci toolbox is free (http://mapageweb.umontreal.ca/gosselif/stat4ci.html); if you use 
% it in your research, please, cite us:
%	Chauvin, A., Worsley, K. J., Schyns, P. G., Arguin, M. & Gosselin, F. (2004).  A sensitive 
%	statistical test for smooth classification images.
% 
% Alan Chauvin & FrŽdŽric Gosselin (frederic.gosselin@umontreal.ca), 20/08/2004

FWHM = sigma * sqrt(8*log(2));