Splitting a string in R, different split argument elements - r

Question

I imported some data with no column names, so now I have just over a million rows, and 1 column (instead of 5 columns).
Each row is formatted like this:
x <- "2012-10-19T16:59:01-07:00 192.101.136.140 <190>Oct 19 2012 23:59:01: %FWSM-6-305011: Built dynamic tcp translation from Inside:10.2.45.62/56455 to outside:192.101.136.224/9874"
strsplit( x , split = c(" ", " ", "%", " "))
and got
[[1]]
[1] "2012-10-19T16:59:01-07:00" "192.101.136.140"
[3] "<190>Oct" "19"
[5] "2012" "23:59:01:"
[7] "%FWSM-6-305011:" "Built"
[9] "dynamic" "tcp"
[11] "translation" "from"
[13] "Inside:10.2.45.62/56455" "to"
[15] "outside:192.101.136.224/9874"
I know that it has to do with recycling the split argument but I can't seem to figure how to get it how I want:
[[1]]
[1] "2012-10-19T16:59:01-07:00" "192.101.136.140"
[3] "<190>Oct 19 2012 23:59:01 "%FWSM-6-305011
[5] Built dynamic tcp translation from Inside:10.2.45.62/56455 to outside:192.101.136.224/9874"
Each row has a different message as the fifth element, but after the 4th element I just want to keep the rest of the string together.
Any help would be appreciated.

Answer 1

You can use paste with the collapse argument to combine every element starting with the fifth element.
A <- strsplit( x = "2012-10-19T16:59:01-07:00 192.101.136.140 <190>Oct 19 2012 23:59:01: %FWSM-6-305011: Built dynamic tcp translation from Inside:10.2.45.62/56455 to outside:192.101.136.224/9874", split = c(" ", " ", "%", " "))
c(A[[1]][1:4], paste(A[[1]][5:length(A[[1]])], collapse=" "))
As #DWin points out, split = c(" ", " ", "%", " ") is not used in order - in other words it's identical to split = c(" ", "%")

Answer 2

I think here you don't need to use strsplit. I use read.table to read the lines using text argument. Then you aggregate columns using paste. Since you have a lot of rows, it is better to do the column aggregation within a data.table.
dt <- read.table(text=x)
library(data.table)
DT <- as.data.table(dt)
DT[ , c('V3','V8') := list(paste(V3,V4,V5),
V8=paste(V8,V9,V10,V11,V12,V13,V14,V15))]
DT[,paste0('V',c(1:3,6:7,8)),with=FALSE]
V1 V2 V3 V6 V7
1: 2012-10-19T16:59:01-07:00 192.101.136.140 <190>Oct 19 2012 23:59:01: %FWSM-6-305011:
V8
1: Built dynamic tcp translation from Inside:10.2.45.62/56455 to outside:192.101.136.224/9874

Answer 3

Here is a function that I think works in the way that you thought strsplit functioned:
split.seq<-function(x,delimiters) {
break.point<-regexpr(delimiters[1], x)
first<-mapply(substring,x,1,break.point-1,USE.NAMES=FALSE)
second<-mapply(substring,x,break.point+1,nchar(x),USE.NAMES=FALSE)
if (length(delimiters)==1) return(lapply(1:length(first),function(x) c(first[x],second[x])))
else mapply(function(x,y) c(x,y),first, split.seq(second, delimiters[-1]) ,USE.NAMES=FALSE, SIMPLIFY=FALSE)
}
split.seq(x,delimiters)
A test:
x<-rep(x,2)
delimiters=c(" ", " ", "%", " ")
split.seq(x,delimiters)
[[1]]
[1] "2012-10-19T16:59:01-07:00"
[2] "192.101.136.140"
[3] "<190>Oct 19 2012 23:59:01: "
[4] "FWSM-6-305011:"
[5] "Built dynamic tcp translation from Inside:10.2.45.62/56455 to outside:192.101.136.224/9874"
[[2]]
[1] "2012-10-19T16:59:01-07:00"
[2] "192.101.136.140"
[3] "<190>Oct 19 2012 23:59:01: "
[4] "FWSM-6-305011:"
[5] "Built dynamic tcp translation from Inside:10.2.45.62/56455 to outside:192.101.136.224/9874"