R - creating rows based upon counter value

Question

input <- read.table(header=F, text=\"abc 2 
                def 3 
                pq 2\")
colnames(input) <- c(\"text\",\"count\")

I have input

Answer 1

by should make quick work of this. Just process the input by row and then join it all up after:

output <- do.call(rbind, by(input, rownames(input), function(x) {
  data.frame(text=rep(x$text, x$count), x$count)
}))
rownames(output) <- NULL
colnames(output) <- c("text","count")
print(output)

##   text count
## 1  abc     2
## 2  abc     2
## 3  def     3
## 4  def     3
## 5  def     3
## 6   pq     2
## 7   pq     2

Answer 2

You could use rep

with(input, {
    data.frame(text = rep(levels(text), count), count = rep(count, count))
})

Or, use a helper function. Both returning the following. inp in the input data

f <- function(j, k) rep(j, k)
data.frame(text = inp$text[f(inp[,1], inp[,2])], count = f(inp[,2], inp[,2]))
#  text count
#1  abc     2
#2  abc     2
#3  def     3
#4  def     3
#5  def     3
#6   pq     2
#7   pq     2

Answer 3

Use row indexing:

input[rep(seq(nrow(input)),input$count),]
# or even
input[rep(rownames(input),input$count),]

#    text count
#1    abc     2
#1.1  abc     2
#2    def     3
#2.1  def     3
#2.2  def     3
#3     pq     2
#3.1   pq     2

The second option works because you can index by the character vector in the rownames as well as colnames, e.g.:

rownames(input)
#[1] "1" "2" "3"
input["1",]
#  text count
#1  abc     2

Answer 4

Using data.table

 library(data.table)
 setDT(input)[, .SD[rep(1:.N, count)]]
 #   text count
 #1:  abc     2
 #2:  abc     2
 #3:  def     3
 #4:  def     3
 #5:  def     3
 #6:   pq     2
 #7:   pq     2

Or

  setDT(input)[input[,rep(1:.N, count)]]

Answer 5

Or

as.data.frame(lapply(input, function(x) rep(x, input$count)))
#   text count
# 1  abc     2
# 2  abc     2
# 3  def     3
# 4  def     3
# 5  def     3
# 6   pq     2
# 7   pq     2