Binomial distribution CDF using scipy.stats.binom.cdf

Question

I wrote below code to use binomial distribution CDF (by using scipy.stats.binom.cdf) to estimate the probability of having NO MORE THAN k heads out of 100 tosses, where k = 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100. and then I tried to plot it using hist().

import scipy
import matplotlib.pyplot as plt
def binomcdf():
    p = 0.5
    n = 100
    x = 0
    for a in range(10):
        print(scipy.stats.binom.cdf(x, n, p))
        x += 10

plt.hist(binomcdf())
plt.show()

but I don't know why my plot returns empty, and I receive below error, can anyone help please!

TypeError: 'NoneType' object is not iterable

score 3 · Answer 1 · answered Oct 11 '17 at 02:06

3

You printed your values, but did not return them. The default return value is None, which produced your error.

answered Oct 11 '17 at 02:06

Davis Herring

36,443
4
48
76

What should I return ? cause even when I added return in the end of my function I get the same error! – Hashmatullah Noorzai Oct 11 '17 at 02:11
@Hazmat: What do you want to plot with `hist()`? You should return that. – Davis Herring Oct 11 '17 at 03:06

score 1 · Accepted Answer · answered Oct 11 '17 at 02:15

1

I would save x and the corresponding cdf output for each associated x to a list, then return that list. Then use the data in the list to make plot.

answered Oct 11 '17 at 02:15

William

83
8

can you please edit your question and add your logic in piece of code, cause I am very new to python, so I will need code wise advice please – Hashmatullah Noorzai Oct 11 '17 at 02:18
something like `mylist = []` – William Oct 12 '17 at 03:22

score 1 · Answer 3 · answered Jul 16 '18 at 11:31

1

You forgot to return calculated values...so you returning None Should work like this- see below- if I got your intent right :)

import scipy
import matplotlib.pyplot as plt
def binomcdf():
    p = 0.5
    n = 100
    x = 0
    result = []
    for a in range(10):
        result.append(scipy.stats.binom.cdf(x, n, p))
        x += 10
    return result

plt.hist(binomcdf())
plt.show()

answered Jul 16 '18 at 11:31

DariaS

51
2

For posterity (or next time I read this answer): Modern scipy wants import scipy.stats not just import scipy. See https://stackoverflow.com/questions/22108017/cannot-use-scipy-stats#22118676 – Ron Jensen Oct 29 '21 at 18:35

score 0 · Answer 4 · answered Dec 17 '21 at 05:50

0

To plot a binomial distribution for every k, you need to store each cdf in an list and return the same list and the same can be used to plot the histogram.

answered Dec 17 '21 at 05:50

Smaurya

167
9

Binomial distribution CDF using scipy.stats.binom.cdf

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