R help - Aug 2010 - SQLDF from Variable Matrix

Dear all,

I would like to do sample statistics, e.g. mean, median from very large
dataset. This is part of commands I use routinely with several dataset
so I would like to make it into function. The simplified examples are

Test<-data.frame(A=c('a','b','c','a','b','c'),B=c(1,2,3,4,5,6))

#Create function (This one work)

GetAvg<-function(Input,Bygroup){
AVG<-fn$sqldf("select A, avg(B) as Average, median(B) as Median
		from Test
    group by $Bygroup")
return(AVG)
}

Result<-GetAvg(Test,'A')

#Create function (This one does not work)

GetAvg<-function(Input,Bygroup){
AVG<-fn$sqldf("select A, avg(B) as Average, median(B) as Median
		from $Input
    group by $Bygroup")
return(AVG)
}

Result<-GetAvg(Test,'A')

The only difference is with $Input. How can I refer to this variable in
sqldf. Thank you


Best Regards,

Suphajak Ngamlak
Equity and Derivatives Trading
Phatra Securities Public Company Limited
Tel: +662-305-9179   
Email: suphajak@phatrasecurities.com



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On Wed, Aug 4, 2010 at 12:29 AM, Suphajak Ngamlak
<Suphajak at phatrasecurities.com> wrote:
> Dear all,
>
> I would like to do sample statistics, e.g. mean, median from very large
> dataset. This is part of commands I use routinely with several dataset
> so I would like to make it into function. The simplified examples are
>
>
Test<-data.frame(A=c('a','b','c','a','b','c'),B=c(1,2,3,4,5,6))
>
> #Create function (This one work)
>
> GetAvg<-function(Input,Bygroup){
> AVG<-fn$sqldf("select A, avg(B) as Average, median(B) as Median
> ? ? ? ? ? ? ? ?from Test
> ? ?group by $Bygroup")
> return(AVG)
> }
>
> Result<-GetAvg(Test,'A')
>
> #Create function (This one does not work)
>
> GetAvg<-function(Input,Bygroup){
> AVG<-fn$sqldf("select A, avg(B) as Average, median(B) as Median
> ? ? ? ? ? ? ? ?from $Input
> ? ?group by $Bygroup")
> return(AVG)
> }
>
> Result<-GetAvg(Test,'A')
That should be GetAvg('Test', 'A') with quotes around Test or if
you
want to be able to specify the data unquoted then insert this line at
the top of your function:

Input <- deparse(substitute(Input))