Word Cloud in R

A word cloud (or tag cloud) can be an handy tool when you need to highlight the most commonly cited words in a text using a quick visualization. Of course, you can use one of the several on-line services, such as wordle or tagxedo , very feature rich and with a nice GUI. Being an R enthusiast, I always wanted to produce this kind of images within R and now, thanks to the recently released Ian Fellows' wordcloud package, finally I can!
In order to test the package I retrieved the titles of the XKCD web comics included in my RXKCD package and produced a word cloud based on the titles' word frequencies calculated using the powerful tm package for text mining (I know, it is like killing a fly with a bazooka!).

library(RXKCD)
library(tm)
library(wordcloud)
library(RColorBrewer)
path <- system.file("xkcd", package = "RXKCD")
datafiles <- list.files(path)
xkcd.df <- read.csv(file.path(path, datafiles))
xkcd.corpus <- Corpus(DataframeSource(data.frame(xkcd.df[, 3])))
xkcd.corpus <- tm_map(xkcd.corpus, removePunctuation)
xkcd.corpus <- tm_map(xkcd.corpus, content_transformer(tolower))
xkcd.corpus <- tm_map(xkcd.corpus, function(x) removeWords(x, stopwords("english")))
tdm <- TermDocumentMatrix(xkcd.corpus)
m <- as.matrix(tdm)
v <- sort(rowSums(m),decreasing=TRUE)
d <- data.frame(word = names(v),freq=v)
pal <- brewer.pal(9, "BuGn")
pal <- pal[-(1:2)]
png("wordcloud.png", width=1280,height=800)
wordcloud(d$word,d$freq, scale=c(8,.3),min.freq=2,max.words=100, random.order=T, rot.per=.15, colors=pal, vfont=c("sans serif","plain"))
dev.off()

As a second example,  inspired by this post from the eKonometrics blog, I created a word cloud from the description of  3177 available R packages listed at http://cran.r-project.org/web/packages.

require(XML)
require(tm)
require(wordcloud)
require(RColorBrewer)
u = "http://cran.r-project.org/web/packages/available_packages_by_date.html"
t = readHTMLTable(u)[[1]]
ap.corpus <- Corpus(DataframeSource(data.frame(as.character(t[,3]))))
ap.corpus <- tm_map(ap.corpus, removePunctuation)
ap.corpus <- tm_map(ap.corpus, content_transformer(tolower))
ap.corpus <- tm_map(ap.corpus, function(x) removeWords(x, stopwords("english")))

ap.corpus <- Corpus(VectorSource(ap.corpus))
ap.tdm <- TermDocumentMatrix(ap.corpus)
ap.m <- as.matrix(ap.tdm)
ap.v <- sort(rowSums(ap.m),decreasing=TRUE)
ap.d <- data.frame(word = names(ap.v),freq=ap.v)
table(ap.d$freq)
pal2 <- brewer.pal(8,"Dark2")
png("wordcloud_packages.png", width=1280,height=800)
wordcloud(ap.d$word,ap.d$freq, scale=c(8,.2),min.freq=3,
max.words=Inf, random.order=FALSE, rot.per=.15, colors=pal2)
dev.off()

As a third example, thanks to Jim's comment, I take advantage of Duncan Temple Lang's RNYTimes package to access user-generate content on the NY Times and produce a wordcloud of 'today' comments on articles.
Caveat: in order to use the RNYTimes package you need a API key from The New York Times which you can get by registering to the The New York Times Developer Network (free of charge) from here.

require(XML)
require(tm)
require(wordcloud)
require(RColorBrewer)
install.packages(packageName, repos = "http://www.omegahat.org/R", type = "source")
require(RNYTimes)
my.key <- "your API key here"
what= paste("by-date", format(Sys.time(), "%Y-%m-%d"),sep="/")
# what="recent"
recent.news <- community(what=what, key=my.key)
pagetree <- htmlTreeParse(recent.news, error=function(...){}, useInternalNodes = TRUE)
x <- xpathSApply(pagetree, "//*/body", xmlValue)
# do some clean up with regular expressions
x <- unlist(strsplit(x, "\n"))
x <- gsub("\t","",x)
x <- sub("^[[:space:]]*(.*?)[[:space:]]*$", "\\1", x, perl=TRUE)
x <- x[!(x %in% c("", "|"))]
ap.corpus <- Corpus(DataframeSource(data.frame(as.character(x))))
ap.corpus <- tm_map(ap.corpus, removePunctuation)
ap.corpus <- tm_map(ap.corpus, content_transformer(tolower))
ap.corpus <- tm_map(ap.corpus, function(x) removeWords(x, stopwords("english")))
ap.tdm <- TermDocumentMatrix(ap.corpus)
ap.m <- as.matrix(ap.tdm)
ap.v <- sort(rowSums(ap.m),decreasing=TRUE)
ap.d <- data.frame(word = names(ap.v),freq=ap.v)
table(ap.d$freq)
pal2 <- brewer.pal(8,"Dark2")
png("wordcloud_NewYorkTimes_Community.png", width=1280,height=800)
wordcloud(ap.d$word,ap.d$freq, scale=c(8,.2),min.freq=2,
max.words=Inf, random.order=FALSE, rot.per=.15, colors=pal2)
dev.off()

Retrieving the author of a script

I know that the best/recommended way to manage the authoring of R code consists in building a package containing a DESCRIPTION file.
Nevertheless, I wrote a very basic function retrieving the name of the authors of a script (or any text file) if these names are written within the first three rows of the file (easily changeable) with this format:

##
## Author:Pinco Palla, Paolino Paperino, Topo Gigio
##

The function:

catch.the.name <- function(filename="myscript.R"){
require(gdata)
str <- scan(filename, what='character', nlines=3, sep="\t", quiet=TRUE)
author <- grep("Author:([^ ]+)", str, value=T)
author <-sub('^.*Author:', "", author)
author <-strsplit(author,",")
author <- trim(author)
return(author[[1]])
}

Replacing Tabs with spaces and back in VIM

Not specifically R-related.
If you need to remove all the blank spaces from a file and replace them with tabs for easy importing in R, you can do it in VIM in no time. In normal mode type:

:set noexpandtab
:%retab!

The full story here

It's not R but It's VERY useful

On the chance that you are talking about replacing a word, say, 500 times in a large text file, you might be interested in sed.

Example (you must be in a unix environment with GNU free software):

sed 's/old_word/new_word/g' text_file > new_text_file

After which, new_text_file will contain the contents of text_file, except with the new_word values in place of the old_word values. For those interested in more detailed information, as usual, man (in this case man sed) is your friend.