[R] suggested method to transform list to a matrix

[David Winsemius]

On Apr 19, 2012, at 1:48 PM, Tim Stutt wrote:

> I have data in the following list format:
>
> USER,VARIABLE,COUNT
> user1, var1, 3
> user1, var2, 4
> user2, var1, 7
> userN, var12, 5
>
> And would like to have it format as a matrix:
>
> 		var1		var2		var12
> user1	3		4
> user2	7
> userN					5
>
> What is the suggested method to do this for 1 million rows, with 12  
> variables and ~ 4,000 unique users?

?xtabs

xtabs( COUNT ~ USER + VARIABLE, data=dfrm )

-- 

David Winsemius, MD
West Hartford, CT