Generate random array of 0 and 1 with a specific ratio

Question

I want to generate a random array of size N which only contains 0 and 1, I want my array to have some ratio between 0 and 1. For example, 90% of the array be 1 and the remainin

Answer 1

You could use a binomial distribution:

np.random.binomial(n=1, p=0.9, size=[1000])

Answer 2

If you want an exact 1:9 ratio:

nums = numpy.ones(1000)
nums[:100] = 0
numpy.random.shuffle(nums)

If you want independent 10% probabilities:

nums = numpy.random.choice([0, 1], size=1000, p=[.1, .9])

or

nums = (numpy.random.rand(1000) > 0.1).astype(int)

Answer 3

Without using numpy, you could do as follows:

import random
percent = 90

nums = percent * [1] + (100 - percent) * [0]
random.shuffle(nums)

Answer 4

Its difficult to get an exact count but you can get approximate answer by assuming that random.random returns a uniform distribution. This is strictly not the case, but is only approximately true. If you have a truly uniform distribution then it is possible. You can try something like the following:

In [33]: p = random.random(10000)
In [34]: p[p <= 0.1] = 0
In [35]: p[p > 0] = 1
In [36]: sum(p == 0)
Out[36]: 997
In [37]: sum(p == 1)
Out[37]: 9003

Hope this helps ...