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

ave can be used to produce the groupwise sum, while keeping the original position:

x[with(x, ave(dummy, name, FUN=sum))>0,]
##    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

ave is something like aggregate but copies the aggregated value for each row in the set:

with(x, ave(dummy, name, FUN=sum))
## [1] 2 2 2 0 0 0 0 0 2 2 2 2