1 ## Copyright (C) 2012 Rik Wehbring
2 ## Copyright (C) 1995-2012 Kurt Hornik
4 ## This file is part of Octave.
6 ## Octave is free software; you can redistribute it and/or modify it
7 ## under the terms of the GNU General Public License as published by
8 ## the Free Software Foundation; either version 3 of the License, or (at
9 ## your option) any later version.
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14 ## General Public License for more details.
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21 ## @deftypefn {Function File} {} logistic_inv (@var{x})
22 ## For each element of @var{x}, compute the quantile (the inverse of
23 ## the CDF) at @var{x} of the logistic distribution.
26 ## Author: KH <Kurt.Hornik@wu-wien.ac.at>
27 ## Description: Quantile function of the logistic distribution
29 function inv = logistic_inv (x)
36 error ("logistic_inv: X must not be complex");
39 if (isa (x, "single"))
40 inv = NaN (size (x), "single");
51 k = (x > 0) & (x < 1);
52 inv(k) = - log (1 ./ x(k) - 1);
58 %! x = [-1 0 0.5 1 2];
59 %!assert(logistic_inv (x), [NaN -Inf 0 Inf NaN]);
61 %% Test class of input preserved
62 %!assert(logistic_inv ([x, NaN]), [NaN -Inf 0 Inf NaN NaN]);
63 %!assert(logistic_inv (single([x, NaN])), single([NaN -Inf 0 Inf NaN NaN]));
65 %% Test input validation
66 %!error logistic_inv ()
67 %!error logistic_inv (1,2)
68 %!error logistic_inv (i)