[R] "subset" or "condition" as argument to a function

[David Winsemius]

On Dec 1, 2009, at 10:38 AM, Santosh wrote:

> Dear R gurus..
> I had tried out some suggestions sent to me privately..and  
> unfortunately,
> they did not work..
>
> To use a condiition in a subset, the associated dataframe needs to be
> attached and detached, which I found cumbersome to use if using more  
> than 1
> dataframe (with different dimensions) with same condition. I would  
> highly
> appreciate your suggestions to overcome this problem.. Please see my  
> example
> of usage I am trying to implement. Please note that the "cond' takes  
> in the
> character instead of logical values...
>
> cond1 <- 'group==1&sales>200'
> cond2 <- 'group==2&sales>200'
> cond3 <- 'group==3&sales>200'

I do not see that you have _ever_ offered a sample dataset in this  
thread, so this suggestion remains untested. Please report what  
happens when you try:

>
> d1 <- subset(dat,subset=eval(parse(text=cond1)))
> plot(y~x,data=dat,subset=eval(parse(text=cond1)),type='b')
> lines(y~x,data=dat,subset=eval(parse(text=cond2)))
> points 
> (y 
> ~ 
> x 
> ,data 
> =dat,subset=eval(parse(text=paste(cond1,cond2)),sep='&'),col='blue')
> points(y~x,data=d1,subset=eval(parse(text=cond3)),col='red')
>
> If I try the above, I get the following error message:
> *Error in subset.data.frame(dat, cond) : 'subset' must evaluate to  
> logical*
>
> If you could also suggest references implementing similar code, I  
> would
> highly appreciate it.

?parse

> Thanks so much,
>
> Santosh
>
> On Mon, Nov 23, 2009 at 6:38 PM, Santosh <santosh2005 at gmail.com>  
> wrote:
>
>> Thanks... I would try it out..
>> -santosh
>>
>>
>> On Sat, Nov 21, 2009 at 12:04 AM, Bernardo Rangel Tura <
>> tura at centroin.com.br> wrote:
>>
>>> On Fri, 2009-11-20 at 17:40 -0800, Santosh wrote:
>>>> Dear Rxperts!
>>>>
>>>> I was wondering if it is possible to write a function which can  
>>>> take in
>>>> argument of a subset or condition.. Of course, I am aware of the
>>> alternate
>>>> methods like coplot, par.plot, xyplot etc... I am specifically
>>> interested in
>>>> using conditions/subsets with "plot"..
>>>>
>>>> A simple fragmented example is shown here..
>>>>
>>>> pltit <- function(y,x,dat,dat1,dat2,sbst) {
>>>> plot(y~x, data=dat, subset=sbst)
>>>> lines(y~x,data=dat1, subset=subst)
>>>> points(y~x,data=dat2,subset=subst)
>>>> }
>>>>
>>>> pltit(profit,weeks,dat=zone1, sbst='group==1&sales>200')
>>>>
>>>> Could you also suggest pointers/references/examples on efficient  
>>>> ways to
>>>> plot simulated data overlaid with observed data?
>>>>
>>>> Have a good weekend!
>>>
>>>
>>
-- 
> .

David Winsemius, MD
Heritage Laboratories
West Hartford, CT