[R] getting numeric arrays from data frame

From: Mark Farnell <mark.farnell_at_gmail.com>
Date: Mon, 07 Apr 2008 15:15:14 +1200

Currently I invoke:

foo <- read.table("foo.data", header=TRUE)

to read a table into foo

Then when I try to plot a histogram out of the 5th column of foo:


It fails and it says:

Error in hist.default(foo[5]) : 'x' must be numeric

Then I tried:


[1] "List"

So how can I get an numeric array out of one of the columns?

Also suppose if the dataframe foo (above) has eight columns and I want to make an x-y scatter plot on two of the columns, how can I extract these two specific columns?



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