[R] selections of data by one variable

[Christoph Lehmann]

test <- data.frame(cbind(1:10,11:20))
names(test) <- c("a", "b")
test[test$b == 17,]
test[test$b %in% c(13, 15, 17),]


Tu Yu-Kang wrote:
> Dear R experts,
> 
> My problem is as follows:
> 
> Suppose I have a data frame d comprising two variable a<-c(1:10) & 
> b<-c(11:20).
> 
> I now want to select a subgroup according the values of b.
> 
> I know if I just want to select, say, b=17, I can use f<-d[d$b==17] and 
> R will give me
>> f
>  a  b
> 7 7 17
> 
> However, if now I want to select a subgroup according to 
> b==e<-c(13,15,17), then the same syntx doesn't work.
> 
> What is the correct way to do it?  My data have more than one million 
> subjects, and I want to select part of them according to their id numbers.
> 
> Your help will be highly appreciated.
> 
> Best regards,
> 
> Yu-Kang
> 
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