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
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14 ## General Public License for more details.
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21 ## @deftypefn {Function File} {} geoinv (@var{x}, @var{p})
22 ## For each element of @var{x}, compute the quantile (the inverse of
23 ## the CDF) at @var{x} of the geometric distribution with parameter @var{p}.
26 ## Author: KH <Kurt.Hornik@wu-wien.ac.at>
27 ## Description: Quantile function of the geometric distribution
29 function inv = geoinv (x, p)
36 [retval, x, p] = common_size (x, p);
38 error ("geoinv: X and P must be of common size or scalars");
42 if (iscomplex (x) || iscomplex (p))
43 error ("geoinv: X and P must not be complex");
46 if (isa (x, "single") || isa (p, "single"))
47 inv = NaN (size (x), "single");
52 k = (x == 1) & (p >= 0) & (p <= 1);
55 k = (x >= 0) & (x < 1) & (p > 0) & (p <= 1);
57 inv(k) = max (ceil (log (1 - x(k)) / log (1 - p)) - 1, 0);
59 inv(k) = max (ceil (log (1 - x(k)) ./ log (1 - p(k))) - 1, 0);
66 %! x = [-1 0 0.75 1 2];
67 %!assert(geoinv (x, 0.5*ones(1,5)), [NaN 0 1 Inf NaN]);
68 %!assert(geoinv (x, 0.5), [NaN 0 1 Inf NaN]);
69 %!assert(geoinv (x, 0.5*[1 -1 NaN 4 1]), [NaN NaN NaN NaN NaN]);
70 %!assert(geoinv ([x(1:2) NaN x(4:5)], 0.5), [NaN 0 NaN Inf NaN]);
72 %% Test class of input preserved
73 %!assert(geoinv ([x, NaN], 0.5), [NaN 0 1 Inf NaN NaN]);
74 %!assert(geoinv (single([x, NaN]), 0.5), single([NaN 0 1 Inf NaN NaN]));
75 %!assert(geoinv ([x, NaN], single(0.5)), single([NaN 0 1 Inf NaN NaN]));
77 %% Test input validation
80 %!error geoinv (1,2,3)
81 %!error geoinv (ones(3),ones(2))
82 %!error geoinv (ones(2),ones(3))