comparison.cloud: Plot a comparison cloud

Description

Plot a cloud comparing the frequencies of words across documents.

Usage

comparison.cloud(term.matrix,scale=c(4,.5), max.words=300,
	random.order=FALSE, rot.per=.1,
	colors=brewer.pal(max(3,ncol(term.matrix)),"Dark2"),
	use.r.layout=FALSE, title.size=3,
	title.colors=NULL, match.colors=FALSE,
	title.bg.colors="grey90", ...)

Arguments

term.matrix

A term frequency matrix whose rows represent words and whose columns represent documents.

scale

A vector of length 2 indicating the range of the size of the words.

max.words

Maximum number of words to be plotted. least frequent terms dropped

random.order

plot words in random order. If false, they will be plotted in decreasing frequency

rot.per

proportion words with 90 degree rotation

colors

Color words in the order of columns in term.matrix

use.r.layout

if false, then c++ code is used for collision detection, otherwise R is used

title.size

Size of document titles

title.colors

Colors used for document titles. See details.

match.colors

Logical: should colors document titles colors match word colors? See details.

title.bg.colors

Colors used for the background of document titles.

...

Additional parameters to be passed to text (and strheight,strwidth).

Value

nothing

Details

Let \(p_{i,j}\) be the rate at which word i occurs in document j, and \(p_j\) be the average across documents(\(\sum_ip_{i,j}/ndocs\)). The size of each word is mapped to its maximum deviation ( \(max_i(p_{i,j}-p_j)\) ), and its angular position is determined by the document where that maximum occurs.

If title.colors is not NULL, it is used for document titles and match.colors is ignored.

Examples

Run this code

# NOT RUN {
if(require(tm)){
	data(SOTU)
	corp <- SOTU
	corp <- tm_map(corp, removePunctuation)
	corp <- tm_map(corp, content_transformer(tolower))
	corp <- tm_map(corp, removeNumbers)
	corp <- tm_map(corp, function(x)removeWords(x,stopwords()))

	term.matrix <- TermDocumentMatrix(corp)
	term.matrix <- as.matrix(term.matrix)
	colnames(term.matrix) <- c("SOTU 2010","SOTU 2011")
	comparison.cloud(term.matrix,max.words=40,random.order=FALSE)
	comparison.cloud(term.matrix,max.words=40,random.order=FALSE,
		title.colors=c("red","blue"),title.bg.colors=c("grey40","grey70"))
	comparison.cloud(term.matrix,max.words=40,random.order=FALSE,
		match.colors=TRUE)

}

# }

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