R help - Jul 2009 - convert factor to indicator matrix

Hi,

I am looking for a function which can convert a single factor (a 
vector), or a list of multiple factors, into the indicator (dummy) 
matrix with 0/1 entries (or other contrasting schemes). I could cook it 
myself, but I am actually sure this thing already exists - but forgot 
the name and package. IIRC it was clearly different from model.matrix, 
because it had a nicer, more straightforward interface [I know how to 
use model.matrix. I just can't figure out the other function any more].

many thanks,
Thomas

On 2/07/2009, at 9:53 AM, Thomas Mang wrote:
> Hi,
>
> I am looking for a function which can convert a single factor (a
> vector), or a list of multiple factors, into the indicator (dummy)
> matrix with 0/1 entries (or other contrasting schemes). I could  
> cook it
> myself, but I am actually sure this thing already exists - but forgot
> the name and package. IIRC it was clearly different from model.matrix,
> because it had a nicer, more straightforward interface [I know how to
> use model.matrix. I just can't figure out the other function any  
> more].
It seems to me that

	m <- model.matrix(~x)

(where x is your factor) is pretty straightforward.  How much simpler
can it get?  The power of the formula concept is working for you here;
it would be hard to do without it.

	cheers,

		Rolf Turner

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