How can I create a histogram in R?

If you put the data in your example into a file, sample.txt, you can then invoke R and do the following:

$ R

Now you're at a R prompt:

> d = read.table('sample.txt',col.name=c("col1","col2","col3"))

You can confirm that the data was loaded correctly into table d using the dim command:

> dim(d)
[1] 21  3

Now you can graph column 3 (col3) as we labeled it above when we read it in from the file, like so:

> hist(d$col3)

Resulting in this plot:

Running it as a single script

If you want you can create the following .r file, call it hist.r:

d = read.table('sample.txt',col.name=c("col1","col2","col3"))
dim(d)
hist(d$col3)

Then run it using R's Rscript command like this:

$ Rscript hist.r
[1] 21  3

This will appear to have done nothing, but it automatically will put a .pdf file in the directory from where you ran it with the contents of the histogram in it.

$ ls -l
total 24
-rw-rw-r-- 1 saml saml    80 Sep 11 02:35 hist.r
-rw-rw-r-- 1 saml saml 12840 Sep 11 02:37 Rplots.pdf
-rw-rw-r-- 1 saml saml   302 Sep 11 02:19 sample.txt

You can customize this so that instead of a .pdf file you'll get a .png file or what have you.

References

• How to plot a graph in R