[R] dummy variables from factors

[Joshua Wiley]

On Tue, Aug 23, 2011 at 10:34 AM, Noah Silverman <noahsilverman at ucla.edu> wrote:
> Hi,
>
> Looking at a large data set with many factors.
>
> I would like to expand each factor variable into multiple new variables for each level. (0,1) coding.
>
> My first though was just to code a big nasty loop, to take each level and cbind a column onto my data set.  But, that seems painful.  There must be a better way.
>
> Is there an "easy" way to do this in R?

Sure, just use model matrix, e.g.:

model.matrix(~ -1 + factor(cyl), data = mtcars)

Cheers,

Josh

>
> (Note, I don't want to internally represent the levels in the data set, but physically have new columns for each level with a binary indicator.)
>
> Thanks!
>
> --
> Noah Silverman
> UCLA Department of Statistics
> 8117 Math Sciences Building
> Los Angeles, CA 90095
>
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-- 
Joshua Wiley
Ph.D. Student, Health Psychology
Programmer Analyst II, ATS Statistical Consulting Group
University of California, Los Angeles
https://joshuawiley.com/