Split vector of strings and paste subset of resulting elements into a new vector

Question

Define

z<- as.character(c(\"1_xx xx xxx_xxxx_12_sep.xls\",\"2_xx xx xxx_xxxx_15_aug.xls\"))

such that

> z
[1] \"1_xx xx x         


        

Answer 1

An alternative along the same lines of @Joran's Answer is this:

foo <- function(x) {
    o <- paste(x[c(1,4,5)], collapse = "_")
    substr(o, 1, nchar(o) - 4) 
}

sapply(strsplit(z, "_"), foo)

The differences are minor - I use collapse = "_" and nchar() but other than that it is similar.

You can write this as a one-liner

sapply(strsplit(z, "_"), 
       function(x) {o <- paste(x[c(1,4,5)], 
                               collapse = "_"); substr(o, 1, nchar(o)-4)})

but writing the custom function to apply is nicer.