unique length of combinations

Question

hi i am working with mtcars data , if mpg=21.0 and cyl=4 ,i want to find how many times the same combination repeated int he data set. i want its frequency

Answer 1

Hello.

You can use the count method of the plyr package to get the frequency. Example:

install.packages('plyr')
library(plyr)
count(mtcars, mpg)

Answer 2

Try this:

sum(mtcars$mpg == 21.0 & mtcars$cyl == 4, na.rm = TRUE)