CODEWITHSUNDEEP
rdata-visualizationfrequency
Ido Tamir
Ido Tamir

Reputation: 198

Frequency table comparison using R

I have two frequency tables created using R's table() function:

freq1 <- table(unlist(strsplit(topic_list1, split=";")))
freq2 <- table(unlist(strsplit(topic_list2, split=";")))

topic_list1 and topic_list2 are strings that contains textual representations of topics separated by ;.

I want a way to compare the two frequencies, graphically if possible.

So if the two lists contain the same topic with different frequencies, I would like to be able to see it. The same goes for topics present in one frequency table, but not in the other.

Upvotes: 3

Views: 1705

Answers (2)

rezakhorshidi
rezakhorshidi

Reputation: 539

You can simply barplot them (with beside=T argument), which will give you a way to visually compare the counts per level ... below is an example:

counts <- table(mtcars$vs, mtcars$gear)
barplot(counts, col=c("darkblue","red"), legend=rownames(counts), beside=T)

Upvotes: 0

gung - Reinstate Monica
gung - Reinstate Monica

Reputation: 11893

There's probably a more elegant way to do this, but this ought to work: 

# here I'm generating some example data
set.seed(5)
topic_list1 <- paste(sample(letters, 20, replace=T), sep=";")
topic_list2 <- paste(sample(letters, 15, replace=T), sep=";")

# I don't make the tables right away
tl1      <- unlist(strsplit(topic_list1, split=";"))
tl2      <- unlist(strsplit(topic_list2, split=";"))
big_list <- unique(c(tl1, tl2))

# this computes your frequencies
lbl         <- length(big_list)
tMat1       <- matrix(rep(tl1, lbl), byrow=T, nrow=lbl)
tMat2       <- matrix(rep(tl2, lbl), byrow=T, nrow=lbl)
tMat1       <- cbind(big_list, tMat1)
tMat2       <- cbind(big_list, tMat2)
counts1     <- apply(tMat1, 1, function(x){sum(x[1]==x[2:length(x)])})
counts2     <- apply(tMat2, 1, function(x){sum(x[1]==x[2:length(x)])})
total_freqs <- rbind(counts1, counts2, counts1-counts2)

# this makes it nice looking & user friendly
colnames(total_freqs) <- big_list
rownames(total_freqs) <- c("topics1", "topics2", "difference")
total_freqs           <- total_freqs[ ,order(total_freqs[3,])]
total_freqs
            d  l  a  z  b f s y m r x h n i g k c v o
topics1     0  0  0  0  0 2 1 1 1 1 2 2 1 1 1 1 2 2 2
topics2     2  2  2  1  1 2 1 1 1 0 1 1 0 0 0 0 0 0 0
difference -2 -2 -2 -1 -1 0 0 0 0 1 1 1 1 1 1 1 2 2 2

From there you could just use the straight numbers or visualize them however you want (e.g, dotplots, etc.). Here's a simple dotplot: 

windows()
  dotchart(t(total_freqs)[,3], main="Frequencies of topics1 - topics2")
  abline(v=0)

enter image description here

Upvotes: 2

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