Calculate percentile for every value in a column of dataframe

Question

I am trying to calculate percentile for every value in column a from a DataFrame x.

Is there a better way to write the following piece of code?

x["pcta"] = [stats.percentileofscore(x["a"].values, i) 
                                    for i in x["a"].values]

I would like to see better performance.

Answer 1

It seems like you want Series.rank():

x.loc[:, 'pcta'] = x.rank(pct=True) # will be in decimal form

Performance:

import scipy.stats as scs

%timeit [scs.percentileofscore(x["a"].values, i) for i in x["a"].values]
1000 loops, best of 3: 877 µs per loop

%timeit x.rank(pct=True)
10000 loops, best of 3: 107 µs per loop