[R] dummy variables from factors

[Noah Silverman]

@Josh  Thanks!  That's exactly what I need.

@ Marc.  I want to do this manually because I want to do many things with the data beyond R's built in functions.  

--
Noah Silverman
UCLA Department of Statistics
8117 Math Sciences Building
Los Angeles, CA 90095

On Aug 23, 2011, at 10:43 AM, Joshua Wiley wrote:

> 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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>> and provide commented, minimal, self-contained, reproducible code.
>> 
> 
> 
> 
> -- 
> Joshua Wiley
> Ph.D. Student, Health Psychology
> Programmer Analyst II, ATS Statistical Consulting Group
> University of California, Los Angeles
> https://joshuawiley.com/