CODEWITHSUNDEEP
pythonpandas
Richard
Richard

Reputation: 65540

How does Pandas calculate quantiles?

I have the following simple dataframe:

> df = pd.DataFrame({'calc_value': [0, 0.081928, 0.94444]})
> df
   calc_value
0    0.000000
1    0.081928
2    0.944440

Why does df.quantile calculate the 90th percentile as 0.7719376? 

> df.quantile(0.9)['calc_value']`
0.7719376

According to my calculations it should be 0.69, via (0.944444-0.081928)*((90-50)/(100-50)).

Upvotes: 1

Views: 1784

Answers (1)

Severin Pappadeux
Severin Pappadeux

Reputation: 20080

Well, step per 0.1 in the range from 0.5...1.0 is equal to (0.94444-0.081928)/5 and is equal to 0.1725024

So 50q is 0.081928
60q is 0.081928+0.1725024=0.25443
70q is 0.081928+2*0.1725024=0.426933
80q is 0.081928+3*0.1725024=0.599435
90q is 0.081928+4*0.1725024=0.771938
100q is 0.081928+5*0.1725024=0.94444

Upvotes: 2

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