Creating a probability distribution using Numpy in Python3.6

Question

I'm trying to create a probability distribution using Numpy in the following way:

x = 3
pat = [0.20, 0.30, 1.30]
z = numpy.random.choice(x, p=numpy.ndarray.tolist(numpy.array(pat)/sum(pat)))

And this works fine. The problem is that my "population" is evolving and starts at 0, meaning that this may happen:

x = 3
pat = [0, 0, 0]
z = numpy.random.choice(x, p=numpy.ndarray.tolist(numpy.array(pat)/sum(pat)))

At which point, python is dividing by 0 and returns an error. Is there anyway to create a probability distribution of this kind?

replace numpy.ndarray.tolist(numpy.array(pat)/sum(pat)) with numpy.ndarray.tolist(numpy.array(pat)/sum(pat)+1e-9).It will make sure that denominator will not be zero but a very very small number. It won't change you answer and not give divide by zero error. — Anubhav Singh
– Anubhav Singh, Commented Nov 26, 2018 at 11:12

zipa · Accepted Answer · 2018-11-26 11:04:40Z

2

In one line it will look like this:

z = numpy.random.choice(x, p=numpy.ndarray.tolist(numpy.array(pat)/sum(pat))) if any(pat) else numpy.random.choice(x)

answered Nov 26, 2018 at 11:04

zipa

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Comments

taras · Accepted Answer · 2018-11-26 10:58:18Z

1

You can use simple if/else for the edge case:

if sum(pat) != 0:
    z = numpy.random.choice(x, p=numpy.ndarray.tolist(numpy.array(pat)/sum(pat)))
else:
    z = numpy.random.choice(x)

answered Nov 26, 2018 at 10:58

taras

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Comments

Dr. Simon Appiah · Accepted Answer · 2022-08-24 00:41:54Z

0

Using python function to find the probability distribution where Sum(pijlog(pin) - sum(pi(log(pi) -sum(on(log(pj))

answered Aug 24, 2022 at 0:41

Dr. Simon Appiah

1

1 Comment

Mike_H Over a year ago

Please use code fences to display code as such. Thank you! Like this Using python function to find the probability distribution where `` Sum(pijlog(pin) - sum(pi(log(pi) -sum(on(log(pj)) ``

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