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| author | Charles Harris <charlesr.harris@gmail.com> | 2018-04-24 19:41:55 -0600 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2018-04-24 19:41:55 -0600 |
| commit | d7d5cb3feccc1fc6cf57159e8b9fe0a733968706 (patch) | |
| tree | ac79b10323eb870c4436811a80b8d10eed3635b2 | |
| parent | a04676a2d1048dc1cc62255547f63c7a17000d02 (diff) | |
| parent | 4373b35379fa11e84a044e5f8bec71ed3e4d50a5 (diff) | |
| download | numpy-d7d5cb3feccc1fc6cf57159e8b9fe0a733968706.tar.gz | |
Merge pull request #10883 from hameerabbasi/nb-doc-fix
DOC: Fix negative binomial documentation.
| -rw-r--r-- | numpy/random/mtrand/mtrand.pyx | 18 |
1 files changed, 8 insertions, 10 deletions
diff --git a/numpy/random/mtrand/mtrand.pyx b/numpy/random/mtrand/mtrand.pyx index 4dabaa093..8ef153c15 100644 --- a/numpy/random/mtrand/mtrand.pyx +++ b/numpy/random/mtrand/mtrand.pyx @@ -3817,7 +3817,7 @@ cdef class RandomState: Draw samples from a negative binomial distribution. Samples are drawn from a negative binomial distribution with specified - parameters, `n` trials and `p` probability of success where `n` is an + parameters, `n` successes and `p` probability of success where `n` is an integer > 0 and `p` is in the interval [0, 1]. Parameters @@ -3837,21 +3837,19 @@ cdef class RandomState: ------- out : ndarray or scalar Drawn samples from the parameterized negative binomial distribution, - where each sample is equal to N, the number of trials it took to - achieve n - 1 successes, N - (n - 1) failures, and a success on the, - (N + n)th trial. + where each sample is equal to N, the number of failures that + occurred before a total of n successes was reached. Notes ----- The probability density for the negative binomial distribution is - .. math:: P(N;n,p) = \\binom{N+n-1}{n-1}p^{n}(1-p)^{N}, + .. math:: P(N;n,p) = \\binom{N+n-1}{N}p^{n}(1-p)^{N}, - where :math:`n-1` is the number of successes, :math:`p` is the - probability of success, and :math:`N+n-1` is the number of trials. - The negative binomial distribution gives the probability of n-1 - successes and N failures in N+n-1 trials, and success on the (N+n)th - trial. + where :math:`n` is the number of successes, :math:`p` is the + probability of success, and :math:`N+n` is the number of trials. + The negative binomial distribution gives the probability of N + failures given n successes, with a success on the last trial. If one throws a die repeatedly until the third time a "1" appears, then the probability distribution of the number of non-"1"s that |