How to create a column and replace value - r

Question

Question
1
An artist impression of a star system is responsible for a nova. The team from university of VYU focus on a class of compounds. The young people was seen enjoying the football match.
2
Scientists have made a breakthrough and solved a decades-old mystery by revealing how a powerful. Heart attacks more due to nurture than nature. SA footballer Senzo Meyiwa shot dead to save girlfriend
Expected output
1 An artist impression of a star system is responsible for a nova.
1 The team from university of VYU focus on a class of compounds.
1 The young people was seen enjoying the foorball match.
2 Scientist have made a breakthrough and solved a decades- old mystery by revealing how a powerful.
2 Heart attacks more due to nurture than nature.
2 SA footballer Senzo Meyiwa shot dead to save girlfriend
The data is in the csv format and it has got around 1000 data points, numbers are in columns(1) and sentence are in column(2). I need to split the string and retain the row number for that particular sentence. Need your help to build the r code
Note: Number and the sentence are two different columns
I have tried this code to string split but i need code for row index
x$qwerty <- as.character(x$qwerty)
sa<-list(strsplit(x$qwerty,".",fixed=TRUE))[[1]]
s<-unlist(sa)
write.csv(s,"C:\\Users\\Suhas\\Desktop\\out23.csv")

Answer 1

One inconvenience of vectorization in R is that they operate from "inside" the vector. That is, they operate on the elements themselves, rather than the elements in the context of the vector. Therefore the user loses the innate ability to keep track of the index, i.e. where element being operated on was located in the original object.
The workaround is to generate the index separately. This is easy to achieve with seq_along, which is an optimized version of 1:length(qwerty). Then you can just paste the index and the results together. In your case, you'll obviously want to do the pasteing before you unlist.

Answer 2

If your dataset is as shown above, may be this helps. You can read from the file as readLines("file.txt")
lines <- readLines(n=7)
1
An artist impression of a star system is responsible for a nova. The team from university of VYU focus on a class of compounds. The young people was seen enjoying the football match.
2
Scientists have made a breakthrough and solved a decades-old mystery by revealing how a powerful. Heart attacks more due to nurture than nature. SA footballer Senzo Meyiwa shot dead to save girlfriend
lines1 <- lines[lines!='']
indx <- grep("^\\d", lines1)
lines2 <- unlist(strsplit(lines1, '(?<=\\.)(\\b| )', perl=TRUE))
indx <- grepl("^\\d+$", lines2)
res <- unlist(lapply(split(lines2,cumsum(indx)),
function(x) paste(x[1], x[-1])), use.names=FALSE)
res
#[1] "1 An artist impression of a star system is responsible for a nova."
#[2] "1 The team from university of VYU focus on a class of compounds."
#[3] "1 The young people was seen enjoying the football match."
#[4] "2 Scientists have made a breakthrough and solved a decades-old mystery by revealing how a powerful."
#[5] "2 Heart attacks more due to nurture than nature."
#[6] "2 SA footballer Senzo Meyiwa shot dead to save girlfriend"
If you want it as 2 column data.frame
dat <- data.frame(id=rep(lines2[indx],diff(c(which(indx),
length(indx)+1))-1), Col1=lines2[!indx], stringsAsFactors=FALSE)
head(dat,2)
# id Col1
#1 1 An artist impression of a star system is responsible for a nova.
#2 1 The team from university of VYU focus on a class of compounds.