Subset n number of rows from a dataframe, based on a categorical variable, in R

Question

I have a dataframe (say x) in R:

> x
Height  Weight Gender
5     60    m
5     70    m
6     80    m
4     90    m
4     60    m
5     70    f
5     80    f
6     60    f
4     90    f
4     60    f

I need an R code that will produce a new dataframe, say y, that takes the subset of X by Gender and only the first three rows of each gender (1:3) to give the result as follows.

>y
Height  Weight Gender
5       60      m
5       70      m
6       80      m
5       70      f
5       80      f
6       60      f

akrun · Accepted Answer · 2015-04-22 16:22:39Z

4

Try slice from dplyr

library(dplyr)
x %>%
    group_by(Gender) %>% 
    slice(1:3)

Or using data.table

library(data.table)
setDT(x)[,.SD[1:3] , Gender]

answered Apr 22, 2015 at 16:22

akrun

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1 Comment

gg-14 Over a year ago

I tried these two packages. And they both give the results correctly. I liked the format of dplyr the best.

lukeA · Accepted Answer · 2015-04-22 16:29:29Z

2

Give by a try:

do.call(rbind, by(X, X$Gender, head, 3))

answered Apr 22, 2015 at 16:29

lukeA

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1 Comment

gg-14 Over a year ago

this was the fastest way to get the result I needed without having to install packages.

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