Random boolean array with fixed number of True and False values

Question

I want to create a 2d array with fixed number of True and False in each row. Here is the code to generate random array of True and False:

np.random.choice(a=[False, True], size=(N, N), p=[p, 1-p])

This code will give me an array of N*N with probability of p for False and 1-p for True. Now I want to set fixed number of False and True in each row, and also random. How can I do it in Python?

Here are some other related questions but are not the same as what I'm asking:

Example in C

Example in C#

Example but without specific number of True and False

Edit: I should add that also this link is not helpful for me as well. As it is seen in my question, I want to have a random boolean 2d array. So creating a 2d array and shuffling it won't be helpful ( shuffle is not shuffling the items independently, it can just move columns or rows), therefore it's not a random array. Please open my questions and let people answer it.

@user2357112 I want to have have the same number of True and False in each row. It's not working — Paniz, Feb 26 '19 at 00:57
"I want to have have the same number of True and False in each row" - that wasn't in your question. — user2357112, Feb 26 '19 at 00:59

score 0 · Answer 1 · answered Mar 20 '19 at 14:56

0

If the wanted number of True (or False) values per row is one and only one :

# size of our array
M = 5 # rows
N = 3 # columns

# create an array full of "False"
foobar = np.full((M,N), False)

# create a list of randomly picked indices, one for each row
idx = np.random.randint(N, size=M)

# replace "False" by "True" at given indices
foobar[range(M), idx] = True

This approach won't work as is for multiple True values per row, though.

answered Mar 20 '19 at 14:56

Skippy le Grand Gourou

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Does it work if we just want one item per row to be False? – Paniz Mar 29 '19 at 23:27
@Paniz Sure, just switch the two occurrences of `True` and `False`. Actually it would work with any couple of values, they don't have to be boolean. – Skippy le Grand Gourou Mar 30 '19 at 09:35
I need to have specific number of True and False in each row. It just works when we have one True ( the rest False) or one False ( the rest True) in each row. – Paniz Apr 03 '19 at 22:55
@Paniz Indeed, and this point was highlighted in the first sentence of my answer. ;) – Skippy le Grand Gourou Apr 04 '19 at 07:54
This may not be the answer to your question, but this is an answer to the question you asked – although it only addresses a particular case. And as such it may prove helpful to part of the people having the same issue – as was I when I found your question. – Skippy le Grand Gourou Apr 04 '19 at 15:37
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True. Thanks a lot – Paniz Apr 04 '19 at 15:48

Random boolean array with fixed number of True and False values

1 Answers1