[R] Discretize factors?

[Daniel Nordlund]

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> On Behalf Of Noah Silverman
> Sent: Saturday, May 15, 2010 11:03 AM
> To: r-help at r-project.org
> Subject: [R] Discretize factors?
> 
> Hi,
> 
> I'm looking for an easy way to discretize factors in R
> 
> I've noticed that the lm function does this automatically with a nice
> result.
> 
> If I have
> 
> group <- c("A", "B","B","C","C","C")
> 
> and run:
> 
> lm(result ~ x1 + group)
> 
> The lm function has split the group into separate binary variables {0,1}
> before performing the regression.  I now have:
> groupA
> groupB
> groupC
> 
> Some of the other models that I want to try won't accept factors, so
> they need to be discretized this way.
> 
> Is there a command in R for this, or some easy shortcut?  (I tried
> digging into the lm code, but couldn't find where this is being done.)
> 
> Thanks!
> 
> -N
> 

Noah,

You might try something like

model.matrix(~ group -1)

Hope this is helpful,

Dan

Daniel Nordlund
Bothell, WA USA