Convert factor to integer

r integer coercion
Jeff Erickson picture Jeff Erickson · Jan 25, 2011 · Viewed 156.2k times · Source

I am manipulating a data frame using the reshape package. When using the melt function, it factorizes my value column, which is a problem because a subset of those values are integers that I want to be able to perform operations on.

Does anyone know of a way to coerce a factor into an integer? Using as.character() will convert it to the correct character, but then I cannot immediately perform an operation on it, and as.integer() or as.numeric() will convert it to the number that system is storing that factor as, which is not helpful.

Thank you!

Jeff

Answer

Aaron left Stack Overflow picture Aaron left Stack Overflow · Jan 25, 2011

Quoting directly from the help page for factor:

To transform a factor f to its original numeric values, as.numeric(levels(f))[f] is recommended and slightly more efficient than as.numeric(as.character(f)).

Related questions

What's the difference between integer class and numeric class in R

I want to preface this by saying I'm an absolute programming beginner, so please excuse how basic this question is. I'm trying to get a better understanding of "atomic" classes in R and maybe this goes for classes in programming …

Read More
Check if the number is integer

I was surprised to learn that R doesn't come with a handy function to check if the number is integer. is.integer(66) # FALSE The help files warns: is.integer(x) does not test if x contains integer numbers! For that, …

Read More
How to catch integer(0)?

Let's say we have a statement that produces integer(0), e.g. a <- which(1:3 == 5) What is the safest way of catching this?

Read More