R help - Apr 2009 - Group by in R

Hi,

I have the following table data:

f1, f2, f3, f4.

I want to compute the counts of unique combinations of f1-f4. In SQL I would
just write:

SELECT COUNT(*) FROM <table> GROUP BY f1, f2, ..,f4.

How to do this in R?

Thanks,

Nick
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Nick Angelou wrote:
> Hi,
>
> I have the following table data:
>
> f1, f2, f3, f4.
>
> I want to compute the counts of unique combinations of f1-f4. In SQL I
would
> just write:
>
> SELECT COUNT(*) FROM <table> GROUP BY f1, f2, ..,f4.
>
> How to do this in R?
table(f1,f2,f3,f4) will give you the counts.

Other statistics can by computed by group using the by() function.

Duncan Murdoch

You can use SQL commands directly on R data frames with the R sqldf package:
See home page:

http://sqldf.googlecode.com

On Mon, Apr 13, 2009 at 6:33 AM, Nick Angelou <nikolay12 at yahoo.com>
wrote:
>
> Hi,
>
> I have the following table data:
>
> f1, f2, f3, f4.
>
> I want to compute the counts of unique combinations of f1-f4. In SQL I
would
> just write:
>
> SELECT COUNT(*) FROM <table> GROUP BY f1, f2, ..,f4.
>
> How to do this in R?
>
> Thanks,
>
> Nick
> --
> View this message in context:
http://www.nabble.com/Group-by-in-R-tp23020587p23020587.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

One way:

g= paste(f1,f2,f3,f4)
table(g)

On Mon, Apr 13, 2009 at 7:33 AM, Nick Angelou <nikolay12 at yahoo.com>
wrote:
>
> Hi,
>
> I have the following table data:
>
> f1, f2, f3, f4.
>
> I want to compute the counts of unique combinations of f1-f4. In SQL I
would
> just write:
>
> SELECT COUNT(*) FROM <table> GROUP BY f1, f2, ..,f4.
>
> How to do this in R?
>
> Thanks,
>
> Nick
> --
> View this message in context:
http://www.nabble.com/Group-by-in-R-tp23020587p23020587.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Mike Lawrence
Graduate Student
Department of Psychology
Dalhousie University

Looking to arrange a meeting? Check my public calendar:
http://tinyurl.com/mikes-public-calendar

~ Certainty is folly... I think. ~

Thanks a lot, guys. Gabor's and Mike's suggestion worked. Duncan's
did not do
exactly what I expected (I guess it's the "paste" in Mike's
that makes
"table" work as I needed it).

One more question - is there a convenient way to order the group by results
as follows:

As rows: the unique combinations of factors f1, f2, f3, as columns the
unique values of f4. The counts are basically the same as of the GROUP BY
statement (or the paste and table combination suggested by Mike).  Only the
way the result is structured is different.

Thanks,
Nick


Nick Angelou wrote:
> 
> Hi,
> 
> I have the following table data:
> 
> f1, f2, f3, f4.
> 
> I want to compute the counts of unique combinations of f1-f4. In SQL I
> would just write:
> 
> SELECT COUNT(*) FROM <table> GROUP BY f1, f2, ..,f4.
> 
> How to do this in R?
> 
> Thanks,
> 
> Nick
> 
-- 
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