group by and filter data management using dplyr

Question

Take a simple dataset

a <- c(1,2,3,4,5,6,7,8)
b <- c(1,2,2,1,2,2,2,2)
c <- c(1,1,1,2,2,2,3,3)
d <- data.frame(a,b,c)

now I want

Answer 1

Try

d %>% 
  group_by(c) %>% 
  filter(any(b == 1))

Which gives:

#Source: local data frame [6 x 3]
#Groups: c
#
#  a b c
#1 1 1 1
#2 2 2 1
#3 3 2 1
#4 4 1 2
#5 5 2 2
#6 6 2 2