Remove group from data.frame if at least one group member meets condition

alternate data.table solution:

setDT(df2)
df2[!(group %in% df2[world == "AF",group])]

gives:

   world place group
1:    AB     1     1
2:    AC     1     1
3:    AD     2     1
4:    AB     1     3
5:    AE     2     3
6:    AC     3     3
7:    AE     1     3

Using keys we can be a bit faster:

setkey(df2,group) 
df2[!J((df2[world == "AF",group]))]

Try

library(dplyr)
df2 %>%
  group_by(group) %>%
  filter(!any(world == "AF"))

Or as per metionned by @akrun:

setDT(df2)[, if(!any(world == "AF")) .SD, group]

Or

setDT(df2)[, if(all(world != "AF")) .SD, group]

Which gives:

#Source: local data frame [7 x 3]
#Groups: group
#
#  world place group
#1    AB     1     1
#2    AC     1     1
#3    AD     2     1
#4    AB     1     3
#5    AE     2     3
#6    AC     3     3
#7    AE     1     3