how to calculate percentile of each 15 rows in python

Question

I have 810 rows in my data frame about vehicle speed and I was trying to calculate the 85th percentile speed for each 15 rows. Here what I did so far:

count = 0
stat1 = []
for i, row in df.iterrows():
    if count == 10:
        stat1 = df.dbl_v.quantile(0.85)
        count = 0
    else:
        count += 1

how can I store and see the 85th percentile speed? It's supposed to be there are 54 of 85th percentile speed.

Thankyou

Answer 1

We can create groups every 15 lines using the remainder of the division by 15

grouper = df.groupby(df.index // 15)

To create a new DF by applying .quantile to multiple columns, we can do this:

df_new = grouper.agg(
               quantile85 = ('dbl_v', lambda x: x.quantile(0.85))
              ,quantile20 = ('other_column', lambda x: x.quantile(0.20))
              ,mean_dbl_v = ('dbl_v', 'mean')
              ,sum_col3 = ('name_column3', 'sum')
               #and so on...
           )