Hi Duncan,
Yes, A and B are columns in D. Having said that I and trying to avoid
tab(D$A,D$B)
and I would prefer:
tab(A,B)
Unfortunately the syntax you suggest is giving me the same error:
Error in eval(expr, envir, enclos) : object "A" not found
I have tried to add some deparse() but I have got the error over again. The
last version I have tried:
function(x,y){
z <- substitute(time ~ x + y, list(x = deparse(substitute(x)), y =
deparse(substitute(y))))
xtabs(z, data=D)
gives me another error:
Error in terms.formula(formula, data = data) :
formula models not valid in ExtractVars
Any idea on how I should modify the function to make it work?
Thanks,
Luca
Il giorno 20/dic/2010, alle ore 19.28, Duncan Murdoch ha scritto:
> On 20/12/2010 1:13 PM, Luca Meyer wrote:
>> I am trying to pass a couple of variable names to a xtabs formula:
>>
>> > tab<- function(x,y){
>> xtabs(time~x+y, data=D)
>> }
>>
>> But when I run:
>>
>> > tab(A,B)
>>
>> I get:
>>
>> Error in eval(expr, envir, enclos) : object "A" not found
>>
>> I am quite sure that there is some easy way out, but I have tried with
>> different combinations of deparse(), substitute(), eval(), etc without
>> success, can someone help?
>
> I assume that A and B are columns in D? If so, you could use
>
> tab(D$A, D$B)
>
> to get what you want. If you really want tab(A,B) to work, you'll need to do
> messy work with substitute, e.g. in the tab function, something like
>
> fla <- substitute(time ~ x + y, list(x = substitute(x), y = substitute(y))
> xtabs(fla, data=D)
>
> Duncan Murdoch
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