What I am trying to do is to load a csv file, and convert to an term-document matrix.
Here is part of my code:
myCorpus<-read.csv('alert-sample-data-4-mining.csv', head=TRUE)
TermDocumentMatrix(myCorpus, control=list(wordLengths=c(1,Inf)))
But get an error message said: Error in UseMethod("TermDocumentMatrix", x) : no applicable method for 'TermDocumentMatrix' applied to an object of class "data.frame"
A few things here -- you're not loading the tm library and you're not creating a corpus. Try something like this (assuming your text data is in a field called "text" in the csv file):
library(tm)
myCorpus <- read.csv("alert-sample-data-4-mining.csv")
corpus <- Corpus(VectorSource(myCorpus$text))
TermDocumentMatrix(corpus)