R subset a data frame with multiple keys [closed]

问题

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Closed 6 years ago.

I have the following data frame

id val
a  1
a  2
a  3
b  4
b  5
c  6

I would like to find a subset of this data frame using a subset of the id's. I know I can do the following if the subset criteria is just 1 value for e.g.

y = subset(x,id=='a')

However how do I get a subset if I have a set of several ids. For example c('a','b'). Doing

y = subset(x,id==c('a','b'))

does not give me what I want.

回答1:

You can subset with logical operators, e.g.

y=subset(x,id=='a' | id=='b')

or you can use the %in% operator:

y=subset(x,id %in% c('a','b'))

回答2:

Try the %in% operator.

> id<-c("a","a","a","b","b","c")
> val<-c(1,2,3,4,5,6)
> x<-data.frame(cbind(id,val))
> subset(x,id %in%c('a','b'))
  id val
1  a   1
2  a   2
3  a   3
4  b   4
5  b   5

来源：https://stackoverflow.com/questions/14465996/r-subset-a-data-frame-with-multiple-keys