indexing - In R, why does deleting rows or cols by empty index results in empty data ? Or, what's the 'right' way to delete?

Question

This is one of the things that really annoys me in R. Consider the following example:

a=data.frame(x=c(1,2),y=c(3,4))
i=which(a$x==0)

At this point, i is "integer(0)" and length(i) is 0. Now if I do:

b=a[-i,]

Because I'm deleting by an empty index, I expect b to have all the data in a. But instead b is an empty data frame. I have to do this instead:

if (length(i)>0) b=a[-i,] else b=a

The same applies to matrices too. Is there a way to delete that handles empty index correctly without the if-else on my part ?

Answer 1

This will solve your example above

 a <- data.frame(x=c(1,2),y=c(3,4))
 b <- a[a$x != 0, ]