differing number of rows in cbind

Question

I am trying to get the frequency of words used in each post, and add them as columns to the training data, the code below is running appropriately for 1 word, for the 2nd word it throws this error.

Function to fetch frequency of a particular word in 1000 posts

word_frequency <- function(w){

  for(i in 2:1000){
    review_text <- paste(Train$Post[i:i], collapse=" ")
    review_source <- VectorSource(review_text)

    corpus <- Corpus(review_source)
    corpus <- tm_map(corpus, content_transformer(tolower))
    corpus <- tm_map(corpus, removePunctuation)
    corpus <- tm_map(corpus, stripWhitespace)
    corpus <- tm_map(corpus, removeWords, stopwords("english"))

    dtm <- DocumentTermMatrix(corpus)
    dtm2 <- as.matrix(dtm)
    frequency <- colSums(dtm2)
    frequency <- frequency[names(frequency) == w]
    frequency <- as.list(frequency)

    freq<-rbind(freq, frequency)
    freq.withNA <- sapply(freq, function(x) ifelse(x == "NULL", NA, x))
  } 
  return(freq)
}

Train <- Training[1:1000,]

Loping over all the words in my wordlist and cbind-ing frequency to the base data frame.

for (w in wordlist) {
  freq <- as.integer()
  new <- word_frequency(w)
  Train <- cbind(Train, new)
  print(paste("Completed word ", w, sep=""))
}