R help - Sep 2007 - How to pass a string as an argument to a function?

I want to pass a predefined string ww ("fa*fb+fc") to function lme so
that I can run

 > lme(y ~  fa*fb+fc, random = ~1|subj, model)

I've tried something like

 > lme(y ~  paste(ww), random = ~1|subj, model)

and

 > lme(y ~  sprintf(ww), random = ~1|subj, model)

but both give me the following error:

Error in model.frame(formula, rownames, variables, varnames, extras,  
extranames,  :
         variable lengths differ (found for 'ww')

There must be a simple way to do this. Any help?

Thanks,
Gang

lme(as.formula(paste("y~",ww)),random=~1|subj,model)


Gang Chen-3 wrote:
> 
> I want to pass a predefined string ww ("fa*fb+fc") to function
lme so
> that I can run
> 
>  > lme(y ~  fa*fb+fc, random = ~1|subj, model)
> 
> There must be a simple way to do this. Any help?
> 
> Thanks,
> Gang
> 
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Yes, as.formula is the magic tool! Thanks a lot...

Gang

On Sep 19, 2007, at 2:00 PM, Vladimir Eremeev wrote:
>
> lme(as.formula(paste("y~",ww)),random=~1|subj,model)
>
>
> Gang Chen-3 wrote:
>>
>> I want to pass a predefined string ww ("fa*fb+fc") to
function lme so
>> that I can run
>>
>>> lme(y ~  fa*fb+fc, random = ~1|subj, model)
>>
>> There must be a simple way to do this. Any help?
>>
>> Thanks,
>> Gang