Calculating Percentile in Python Pandas Dataframe

Question

I'm trying to calculate the percentile of each number within a dataframe and add it to a new column called 'percentile'.

This is my attempt:

import pandas as pd
from scipy import stats

data = {'symbol':'FB','date':['2012-05-18','2012-05-21','2012-05-22','2012-05-23'],'close':[38.23,34.03,31.00,32.00]}

df = pd.DataFrame(data)

close = df['close']

for i in df:
    df['percentile'] = stats.percentileofscore(close,df['close'])

The column is not being filled and results in 'NaN'. This should be fairly easy, but I'm not sure where I'm going wrong.

Thanks in advance for the help.

Answer 1

df.close.apply(lambda x: stats.percentileofscore(df.close.sort_values(),x))

or

df.close.rank(pct=True)

Output:

0    1.00
1    0.75
2    0.25
3    0.50
Name: close, dtype: float64