Dearest community,
If this is my input:
ID TASK
1 a
1 a
1 b
2 a
2 c
2 a
Then would like to group the ID's and have a code such that a can loop through the tasks per subgroup. If a particular subgroup has a specific task I will remove it.
For example, the rule can be: delete complete subgroup if it contains a task c. Then in the example above, the complete ID=2 is removed and only ID=1 is returned with all its tasks, like:
ID TASK
1 a
1 a
1 b
Obviously, my real dataset is enourmous, and I would like to find a code that is easily to adapt to screen for different kinds of tasks (but same kind of idea).
And, as you may have guessed, I am a very new to coding and R. So I am very very gratefull with your help! And a simple solution would be awesome!
If it can be a continuation of the following, that would be great, since I probably would understand it the best than 
library(dplyr)
df %>%
arrange(ID) %>%
group_by(ID) %>%
...help... 
Thanks a million!!!