[Numpy-discussion] Numpy newbie question: matrix creation

[Robert Kern]

On Wed, Sep 25, 2013 at 1:12 PM, Edmondo Porcu <edmondo.porcu at gmail.com>
wrote:
>
> That's what I was looking for, except that I want to be sure to generate
all the possible combinations, and to have no repeated values.

Okay, then you need to find all of the integer partitions of 10 with
`ncols` elements (padding with 0s for those partitions with fewer than
`ncols` elements), finding the permutations of each padded partition, then
eliminating duplicates.


import itertools
import numpy as np


def gen_partitions(n):
    """ Generate integer partitions for `n`.

    http://homepages.ed.ac.uk/jkellehe/partitions.php
    """
    a = [0 for i in range(n + 1)]
    k = 1
    y = n - 1
    while k != 0:
        x = a[k - 1] + 1
        k -= 1
        while 2*x <= y:
            a[k] = x
            y -= x
            k += 1
        l = k + 1
        while x <= y:
            a[k] = x
            a[l] = y
            yield a[:k + 2]
            x += 1
            y -= 1
        a[k] = x + y
        y = x + y - 1
        yield a[:k + 1]


def gen_permuted_partitions(ncols, n=10):
    for partition in gen_partitions(n):
        partition = list(partition)
        if len(partition) > ncols:
            continue
        partition.extend([0] * (ncols - len(partition)))
        for x in itertools.permutations(partition):
            yield x


def compute_matrix(ncols):
    return np.array(sorted(set(gen_permuted_partitions(ncols)))) / 10.0

--
Robert Kern
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