r - How to extract data from a data table in R

Question

I am asking a pretty basic question: how to pull out "Female" data from this table and calculating average number for "Females" using R. Two columns 1. sex 2. height

sex    height
Male   75.00000
Male   70.00000
Female 65.00000
Female 66.00000

Thanks a lot!

标签： raggregate

Answer 1

如果您使用的是 data.table，请使用此

dt[,avg:=mean(height),by=.(sex)]