How to count the number of observations in R like Stata command count

Question

aaa<- data.frame(sex=c(1,1,2,2,1,1), group1=c(1,2,1,2,2,2),group2=c(\"A\",\"B\",\"A\",\"B\",\"A\",\"B\"))

stata command:

count if se         


        

Answer 1

You can also use the filter function from the dplyr package which returns rows with matching conditions.

> library(dplyr)

> nrow(filter(aaa, sex == 1 & group1 == 2))
[1] 3
> nrow(filter(aaa, sex == 1 & group2 == "A"))
[1] 2