Hi, I have a large series of numbers saved in one column
[34,5,21,98,34,3,432,55,27,90,1125,......]. These data are indexed, e.g. by
[1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,......N] which are in another column.

Basically I am calculating the 25% percentiles for numbers indexed "1", "2",
"3",...., "N" respectivelly. There are a lot of numbers with a big uplimit of
index "N" so that selecting numbers of each index manually is not easy.

In another word, if N = 9999, then I need to calculate N 25% percentiles
with one for each indexed number class. That is it. Thansk for any input!








Thanks a lot!