/usr/share/psychtoolbox-3/PsychProbability/CoinFlip.m is in psychtoolbox-3-common 3.0.9+svn2579.dfsg1-1.
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | function x = CoinFlip(ndraws,p)
% x = CoinFlip(ndraws,p)
%
% Generate a list x of zeros and ones according to coin flipping (i.e.
% Bernoulli) statistics with probability p of getting a 1.
% 1/20/97 dhb Delete obsolet rand('uniform').
% 7/24/04 awi Cosmetic.
% Generate ndraws random variables on the real
% interval [0,1).
unif = rand(ndraws,1);
% Find all of the ones that are less than p.
% On average, this proportion will be p.
index = find(unif < p);
[nones,m] = size(index);
% Generate an array of zeros and then set
% the ones found in the previous step to 1.
x = zeros(ndraws,1);
if (nones ~= 0)
x(index) = ones(nones,m);
end
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