[R] Factor levels.

[Rolf Turner]

On 4/10/2007, at 7:50 AM, Peter Dalgaard wrote:

> Rolf Turner wrote:
>>> Does it even work? (What if it is the first or the 2nd level that  
>>> is absent?
>>
>>     Yes it works.  What's the problem?
>>
>>     To beat it to death:  if the second level of fff is absent  
>> then fff will consist entirely of 1's and 3's,
>>     and so c("U","A","S")[fff] will consist entirely of U's and  
>> S's.  I can then set the levels to be
>>     c("U","A","S") and get what I want.
> You didn't say that fff was numeric.

	All factors are numeric.
> If fff is a factor, then we have the problem:
>
> > attach(read.table(stdin(),header=T))
> 0: fff
> 1: Unit
> 2: Scholarship
> 3: Scholarship
> 4: Unit
> 5:
> > c("U","A","S")[fff]
> [1] "A" "U" "U" "A"

	My original fff is a factor with levels c 
("Unit","Achievement","Scholarship").  If you make that
	adjustment, you get the ``right answer''.
> Actually we have another problem too, namely sort order....

	No, there is no sort order problem.  See above.

	[Given that the original fff has its levels in the order specified  
then Unit maps to U,
	Achievement to A, and Scholarship to S.]

				cheers,

					Rolf

	P.S.  ***Are*** there any risks/dangers in following Christos  
Hatzis' suggestion of simply doing

			levels(fff) <- c("U","A","S")       ???

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