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

Consider df is your data.frame, then use tapply and [ to subset what you want:

> ind <- with(df, tapply(dummy, name, sum))
> df[df$name %in% names(ind)[ind!=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

Another alternative:

> result <- split(df, df$name)[with(df, tapply(dummy, name, function(x) sum(x)!=0))]
> do.call(rbind, result)