How to select rows according to column value conditions

Question

I have a data set which looks like the following (partially):

id  name    dummy
1   Jane    1
1   Jane    0
1   Jane    1
2   Mike    0
2   Mike    0
2   Mik         


        

Answer 1

A possible solution:

subset(dat, as.logical(ave(dummy, id, FUN = any)))

#    id name dummy
# 1   1 Jane     1
# 2   1 Jane     0
# 3   1 Jane     1
# 9   3  Tom     1
# 10  3  Tom     1
# 11  3  Tom     0
# 12  3  Tom     0

An alternative with data.table:

library(data.table)
setDT(dat)[, if (any(dummy)) .SD, by = id]

Or with dplyr:

library(dplyr)
dat %>% 
  group_by(id) %>% 
  filter(any(dummy))