R tm package vcorpus: Error in converting corpus to data frame

Question

I am using the tm package to clean up some data using the following code:

mycorpus <- Corpus(VectorSource(x))
mycorpus <- tm_map(mycorpus, removePunctuation)

I then want to convert the corpus back into a data frame in order to export a text file that contains the data in the original format of a data frame. I have tried the following:

dataframe <- as.data.frame(mycorpus)

But this returns an error:

"Error in as.data.frame.default.(mycorpus) : cannot coerce class "c(vcorpus, > corpus")" to a data.frame

How can I convert a corpus into a data frame?

Solution 1

Your corpus is really just a character vector with some extra attributes. So it's best to convert it to character, then you can save that to a data.frame like so:

library(tm)
x <- c("Hello. Sir!","Tacos? On Tuesday?!?")
mycorpus <- Corpus(VectorSource(x))
mycorpus <- tm_map(mycorpus, removePunctuation)

dataframe <- data.frame(text=unlist(sapply(mycorpus, `[`, "content")), 
    stringsAsFactors=F)

which returns

              text
1        Hello Sir
2 Tacos On Tuesday

UPDATE: With newer version of tm, they seem to have updated the as.list.SimpleCorpus method which really messes with using sapplyand lapply. Now I guess you'd have to use

dataframe <- data.frame(text=sapply(mycorpus, identity), 
    stringsAsFactors=F)

Solution 2

The Corpus classed objected has a content attribute accessible through get:

library("tm")

x <- c("Hello. Sir!","Tacos? On Tuesday?!?")
mycorpus <- Corpus(VectorSource(x))
mycorpus <- tm_map(mycorpus, removePunctuation)

attributes(mycorpus)
# $names
# [1] "content" "meta"    "dmeta"  
# 
# $class
# [1] "SimpleCorpus" "Corpus"      
# 

df <- data.frame(text = get("content", mycorpus))

head(df)
#               text
# 1        Hello Sir
# 2 Tacos On Tuesday

Solution 3

You can convert to data.frame, sort the most frequent words and plot in a wordcloud!

library(tm)
library("wordcloud")
library("RColorBrewer")

x <- c("Hello. Sir!","Tacos? On Tuesday?!?", "Hello")
mycorpus <- Corpus(VectorSource(x))
mycorpus <- tm_map(mycorpus, removePunctuation)

dtm <- TermDocumentMatrix(mycorpus)
m <- as.matrix(dtm)
v <- sort(rowSums(m),decreasing=TRUE)
d <- data.frame(word = names(v),freq=v)
head(d, 10)

#           word freq
#hello     hello    2
#sir         sir    1
#tacos     tacos    1
#tuesday tuesday    1

#plot in a wordcloud
set.seed(1234)
wordcloud(words = d$word, freq = d$freq, min.freq = 1,
          max.words=200, random.order=FALSE, rot.per=0.35, 
          colors=brewer.pal(8, "Dark2"))

Solution 4

The older answer posted by MrFlick works only in previous version on tm, I was able to fix it by removing content from the formula.

dataframe<-data.frame(text=unlist(sapply(mycorpus, `[`)), stringsAsFactors=F)

View more solutions

Comments

[lmcshane]

thanks! I see the return as a data.frame that has a list with summary data included in the first instance? (1 list(list(content = "Hello Sir", meta = list(author...)

[Tyler Rinker]

Odd, I am using tm version 0.6 (on CRAN currently) and Flick's answer works for me.

[myloginid]

Hello - I get this error in the conversion. Any Idea why? > data.frame(text=unlist(sapply(ccorpus_clean, [, "content")), stringsAsFactors=F) Error in UseMethod("meta", x) : no applicable method for 'meta' applied to an object of class "try-error"