One way to do it is to use the magic n()
function within filter
:
library(dplyr)
my_data <- data.frame(Year=1996, Site="A", Brood=c(1,1,2,2,2))
my_data %>%
group_by(Year, Site, Brood) %>%
filter(n() >= 3)
The n()
function gives the number of rows in the current group (or the number of rows total if there is no grouping).