strsplit by variable separator

Question

I have some strings of data separated by " " that needs to be split into columns. Is there an easy way to split the data by every nth separator. For example, the first value in x tells you that the first 4 values in y correspond to the first trial. The second value in x tells you that the next 3 values in y correspond to the second trial, and so on.

x <- c("4 3 3", "3 3 3 2 3")
y <- c("110 88 77 66 55 44 33 22 33 44 11 22 11", "44 55 66 33 22 11 22 33 44 55 66 77 88 66 77 88")

The goal is something like this:

structure(list(session = 1:2, trial.1 = structure(1:2, .Label = c("110 88 77", 
"44 55 66"), class = "factor"), trial.2 = structure(c(2L, 1L), .Label = c("33 22 11", 
"66 55 44"), class = "factor"), trial.3 = structure(1:2, .Label = c("22 33 44", 
"23 33 44"), class = "factor"), trial.4 = structure(c(NA, 1L), .Label = "55 66", class = "factor"), 
    trial.5 = structure(c(NA, 1L), .Label = "77 88 66", class = "factor")), .Names = c("session", 
"trial.1", "trial.2", "trial.3", "trial.4", "trial.5"), class = "data.frame", row.names = c(NA, 
-2L))

Ideally, any extra values from y need to be dropped from the resulting data frame, and the uneven row lengths should be filled with NA's.

Answer 1

This maybe useful

dumx<-strsplit(x,' ')
dumy<-strsplit(y,' ')
dumx<-lapply(dumx,function(x)(cumsum(as.numeric(x))))
dumx<-lapply(dumx,function(x){mapply(seq,c(1,x+1)[-(length(x)+1)],x,SIMPLIFY=FALSE)})
ans<-mapply(function(x,y){lapply(x,function(w,z){z[w]},z=y)},dumx,dumy)

I will leave you to convert the resulting list to dataframe :)