how to read text in a table from a csv file

Question

I am new using the tm package. I want to read a csv file which contents one column with 2000 texts and a second column with a factor variable yes/no into a Corpus. My intention is to convert the text as a matrix and use the factor variable as target for prediction. I would need to divide the corpus in train and test sets as well. I read several documents like tm.pdf etc. and found the documentation relatively limited. This is my attempt following another threat on the same subject,

TexTest<-read.csv("C:/Test.csv")
 m <- list(Text = "Text", Clasification = "Classification")
 corpus1 <-
Corpus(x=TexTest,readerControl=list(reader=readTabular(mapping=m),language="en"))

Error in if (x$Length > 0) vector("list", as.integer(x$Length)) else list() : 
  argument is of length zero

Using

corpus1 <- Corpus(VectorSource(TexTest))

results in

A corpus with 2 text documents

instead of 2000 texts.

How is the standard procedure here? Thanks

Answer 1

Jus a note that readTabular is gone in the tm release on Dec 2017 as described in https://cran.r-project.org/web/packages/tm/news.html

Changes in tm version 0.7-2
SIGNIFICANT USER-VISIBLE CHANGES
DataframeSource now only processes data frames with the two mandatory columns "doc_id" and "text". Additional columns are used as document level metadata. This implements compatibility with Text Interchange Formats corpora (https://github.com/ropensci/tif).

readTabular() has been removed. Use DataframeSource instead.

Answer 2

There is an error with Ben's code, probably due to tm package update.

m <- list(Content = "Text", Topic = "Classification")

the upper case "Content" is wrong. It should be lower case. Lower case "content" is a reserved word in tm package to assign the text column to be THE content you can call from corpus object.

m <- list(content = "Text", Topic = "Classification")

If you use the first line of error code, you will still proceed without error message. But "Content" is a name that tm package reads as a special name you assign to meta information.

Answer 3

You need to use DataframeSource in the Corpus function, that's where your example differs from the example on p. 2 of the PDF Extensions: How to Handle Custom File Formats in the tm package.

Some reproducible data:

TexTest <- structure(list(Text = c("When discussing performance with colleagues, teaching, sending a bug report or searching for guidance on mailing lists and here on SO, a reproducible example is often asked and always helpful. What are your tips for creating an excellent example? How do you paste data structures from r in a text format? What other information should you include? Are there other tricks in addition to using dput(), dump() or structure()? When should you include library() or require() statements? Which reserved words should one avoid, in addition to c, df, data, etc? How does one make a great r reproducible example?", 
"Sometimes the problem really isn't reproducible with a smaller piece of data, no matter how hard you try, and doesn't happen with synthetic data (although it's useful to show how you produced synthetic data sets that did not reproduce the problem, because it rules out some hypotheses). Posting the data to the web somewhere and providing a URL may be necessary. If the data can't be released to the public at large but could be shared at all, then you may be able to offer to e-mail it to interested parties (although this will cut down the number of people who will bother to work on it). I haven't actually seen this done, because people who can't release their data are sensitive about releasing it any form, but it would seem plausible that in some cases one could still post data if it were sufficiently anonymized/scrambled/corrupted slightly in some way. If you can't do either of these then you probably need to hire a consultant to solve your problem", 
"You are most likely to get good help with your R problem if you provide a reproducible example. A reproducible example allows someone else to recreate your problem by just copying and pasting R code. There are four things you need to include to make your example reproducible: required packages, data, code, and a description of your R environment. Packages should be loaded at the top of the script, so it's easy to see which ones the example needs. The easiest way to include data in an email is to use dput() to generate the R code to recreate it. For example, to recreate the mtcars dataset in R, I'd perform the following steps: Run dput(mtcars) in R Copy the output In my reproducible script, type mtcars <- then paste. Spend a little bit of time ensuring that your code is easy for others to read: make sure you've used spaces and your variable names are concise, but informative, use comments to indicate where your problem lies, do your best to remove everything that is not related to the problem. The shorter your code is, the easier it is to understand. Include the output of sessionInfo() as a comment. This summarises your R environment and makes it easy to check if you're using an out-of-date package. You can check you have actually made a reproducible example by starting up a fresh R session and pasting your script in. Before putting all of your code in an email, consider putting it on http://gist.github.com/. It will give your code nice syntax highlighting, and you don't have to worry about anything getting mangled by the email system.", 
"Do your homework before posting: If it is clear that you have done basic background research, you are far more likely to get an informative response. See also Further Resources further down this page. Do help.search(keyword) and apropos(keyword) with different keywords (type this at the R prompt). Do RSiteSearch(keyword) with different keywords (at the R prompt) to search R functions, contributed packages and R-Help postings. See ?RSiteSearch for further options and to restrict searches. Read the online help for relevant functions (type ?functionname, e.g., ?prod, at the R prompt) If something seems to have changed in R, look in the latest NEWS file on CRAN for information about it. Search the R-faq and the R-windows-faq if it might be relevant (http://cran.r-project.org/faqs.html) Read at least the relevant section in An Introduction to R If the function is from a package accompanying a book, e.g., the MASS package, consult the book before posting. The R Wiki has a section on finding functions and documentation", 
"Before asking a technical question by e-mail, or in a newsgroup, or on a website chat board, do the following:  Try to find an answer by searching the archives of the forum you plan to post to. Try to find an answer by searching the Web. Try to find an answer by reading the manual. Try to find an answer by reading a FAQ. Try to find an answer by inspection or experimentation. Try to find an answer by asking a skilled friend. If you're a programmer, try to find an answer by reading the source code. When you ask your question, display the fact that you have done these things first; this will help establish that you're not being a lazy sponge and wasting people's time. Better yet, display what you have learned from doing these things. We like answering questions for people who have demonstrated they can learn from the answers. Use tactics like doing a Google search on the text of whatever error message you get (searching Google groups as well as Web pages). This might well take you straight to fix documentation or a mailing list thread answering your question. Even if it doesn't, saying “I googled on the following phrase but didn't get anything that looked promising” is a good thing to do in e-mail or news postings requesting help, if only because it records what searches won't help. It will also help to direct other people with similar problems to your thread by linking the search terms to what will hopefully be your problem and resolution thread. Take your time. Do not expect to be able to solve a complicated problem with a few seconds of Googling. Read and understand the FAQs, sit back, relax and give the problem some thought before approaching experts. Trust us, they will be able to tell from your questions how much reading and thinking you did, and will be more willing to help if you come prepared. Don't instantly fire your whole arsenal of questions just because your first search turned up no answers (or too many). Prepare your question. Think it through. Hasty-sounding questions get hasty answers, or none at all. The more you do to demonstrate that having put thought and effort into solving your problem before seeking help, the more likely you are to actually get help. Beware of asking the wrong question. If you ask one that is based on faulty assumptions, J. Random Hacker is quite likely to reply with a uselessly literal answer while thinking Stupid question..., and hoping the experience of getting what you asked for rather than what you needed will teach you a lesson."
), Classification = c("Yes", "No", "Yes", "No", "Yes")), .Names = c("Text", 
"Classification"), class = "data.frame", row.names = c(NA, -5L
))

Make a corpus of five documents (one for each row in the CSV file)

# TexTest<-read.csv("Test.csv", stringsAsFactors = FALSE)
m <- list(Content = "Text", Topic = "Classification")
library(tm)
myReader <- readTabular(mapping = m)
(corpus <- Corpus(DataframeSource(TexTest), readerControl = list(reader = myReader)))

A corpus with 5 text documents
# as expected, one doc per row of the CSV file

corpus[[1]]

When discussing performance with colleagues, teaching, sending a bug report or searching for guidance on mailing lists and here on SO, a reproducible example is often asked and always helpful. What are your tips for creating an excellent example? How do you paste data structures from r in a text format? What other information should you include? Are there other tricks in addition to using dput(), dump() or structure()? When should you include library() or require() statements? Which reserved words should one avoid, in addition to c, df, data, etc? How does one make a great r reproducible example?

# as expected, the first row of the CSV file

Is that what you wanted to do?