scipy.special.comb

scipy.special.comb(N, k, exact=False, repetition=False)

The number of combinations of N things taken k at a time.

This is often expressed as “N choose k”.

Parameters:

N : int, ndarray

Number of things.

k : int, ndarray

Number of elements taken.

exact : bool, optional

If exact is False, then floating point precision is used, otherwise exact long integer is computed.

repetition : bool, optional

If repetition is True, then the number of combinations with repetition is computed.

Returns:

val : int, ndarray

The total number of combinations.

Notes

• Array arguments accepted only for exact=False case.
• If k > N, N < 0, or k < 0, then a 0 is returned.

Examples

>>> from scipy.special import comb
>>> k = np.array([3, 4])
>>> n = np.array([10, 10])
>>> comb(n, k, exact=False)
array([ 120.,  210.])
>>> comb(10, 3, exact=True)
120L
>>> comb(10, 3, exact=True, repetition=True)
220L