1 ## Copyright (C) 2012 Rik Wehbring
2 ## Copyright (C) 1995-2012 Kurt Hornik
4 ## This file is part of Octave.
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7 ## under the terms of the GNU General Public License as published by
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21 ## @deftypefn {Function File} {} binoinv (@var{x}, @var{n}, @var{p})
22 ## For each element of @var{x}, compute the quantile (the inverse of
23 ## the CDF) at @var{x} of the binomial distribution with parameters
24 ## @var{n} and @var{p}, where @var{n} is the number of trials and
25 ## @var{p} is the probability of success.
28 ## Author: KH <Kurt.Hornik@wu-wien.ac.at>
29 ## Description: Quantile function of the binomial distribution
31 function inv = binoinv (x, n, p)
37 if (!isscalar (n) || !isscalar (p))
38 [retval, x, n, p] = common_size (x, n, p);
40 error ("binoinv: X, N, and P must be of common size or scalars");
44 if (iscomplex (x) || iscomplex (n) || iscomplex (p))
45 error ("binoinv: X, N, and P must not be complex");
48 if (isa (x, "single") || isa (n, "single") || isa (p, "single"));
49 inv = zeros (size (x), "single");
51 inv = zeros (size (x));
54 k = (!(x >= 0) | !(x <= 1) | !(n >= 0) | (n != fix (n)) |
55 !(p >= 0) | !(p <= 1));
58 k = find ((x >= 0) & (x <= 1) & (n >= 0) & (n == fix (n)
59 & (p >= 0) & (p <= 1)));
61 if (isscalar (n) && isscalar (p))
62 cdf = binopdf (0, n, p) * ones (size (k));
63 while (any (inv(k) < n))
64 m = find (cdf < x(k));
66 inv(k(m)) = inv(k(m)) + 1;
67 cdf(m) = cdf(m) + binopdf (inv(k(m)), n, p);
73 cdf = binopdf (0, n(k), p(k));
74 while (any (inv(k) < n(k)))
75 m = find (cdf < x(k));
77 inv(k(m)) = inv(k(m)) + 1;
78 cdf(m) = cdf(m) + binopdf (inv(k(m)), n(k(m)), p(k(m)));
90 %! x = [-1 0 0.5 1 2];
91 %!assert(binoinv (x, 2*ones(1,5), 0.5*ones(1,5)), [NaN 0 1 2 NaN]);
92 %!assert(binoinv (x, 2, 0.5*ones(1,5)), [NaN 0 1 2 NaN]);
93 %!assert(binoinv (x, 2*ones(1,5), 0.5), [NaN 0 1 2 NaN]);
94 %!assert(binoinv (x, 2*[0 -1 NaN 1.1 1], 0.5), [NaN NaN NaN NaN NaN]);
95 %!assert(binoinv (x, 2, 0.5*[0 -1 NaN 3 1]), [NaN NaN NaN NaN NaN]);
96 %!assert(binoinv ([x(1:2) NaN x(4:5)], 2, 0.5), [NaN 0 NaN 2 NaN]);
98 %% Test class of input preserved
99 %!assert(binoinv ([x, NaN], 2, 0.5), [NaN 0 1 2 NaN NaN]);
100 %!assert(binoinv (single([x, NaN]), 2, 0.5), single([NaN 0 1 2 NaN NaN]));
101 %!assert(binoinv ([x, NaN], single(2), 0.5), single([NaN 0 1 2 NaN NaN]));
102 %!assert(binoinv ([x, NaN], 2, single(0.5)), single([NaN 0 1 2 NaN NaN]));
104 %% Test input validation
107 %!error binoinv (1,2)
108 %!error binoinv (1,2,3,4)
109 %!error binoinv (ones(3),ones(2),ones(2))
110 %!error binoinv (ones(2),ones(3),ones(2))
111 %!error binoinv (ones(2),ones(2),ones(3))
112 %!error binoinv (i, 2, 2)
113 %!error binoinv (2, i, 2)
114 %!error binoinv (2, 2, i)