/usr/share/psychtoolbox-3/Psychometric/InvertLogistic.m is in psychtoolbox-3-common 3.0.11.20140816.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 | function x = InvertLogistic(y,a,b);
% x = InvertLogistic(y,a,b);
%
% Compute the inverse of a logistic equation.
% The form of the logistic equation is y = 1/(1+10^-(ax+b)).
%
% See also: ComputeLogistic, FitLogistic, FitLogitYN.
%
% 2/15/95 dhb Wrote it.
% Enforce range sanity
if (y == 1)
y = 0.99;
elseif (y == 0)
y = 0.01;
end
% Now invert the equation
axb = -1*log10( (1-y)/y );
x = (axb-b)/a;
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