[R] Unique?

[Francisco J. Zagmutt]

If you only care about the sum of CONVUNIT by each TRIPID then you can use 
tapply i.e.:

step4<-data.frame(TRIPID=rep(c(111,222,333),3),CONVUNIT=rpois(9,40))
result<-tapply(step4$CONVUNIT,INDEX=step4$TRIPID,FUN=sum)
result
111 222 333
115 107 123

Is this what you wanted to do?  I can't think of anything faster than tapply 
for your problem.

I hope this helps

Francisco




>From: "Guenther, Cameron" <Cameron.Guenther at MyFWC.com>
>To: <r-help at stat.math.ethz.ch>
>Subject: [R] Unique?
>Date: Wed, 10 May 2006 17:02:33 -0400
>
>
>Hello,
>I have sample data set that looks like:
>
>YEAR	MONTH	DAY	CONTINUE	SPL		TIMEFISH
>TIMEUNIT	AREA	COUNTY	DEPTH	DEPUNIT	GEAR		TRIPID
>CONVUNIT
>1992	1	26	1		SP0073928	8
>H		7	25		4	NA		1000000
>02163399054	161
>1992	1	26	1		SP0073928	8
>H		7	25		4	NA		1000000
>02163399054	8
>1992	1	26	2		SP0004228	8
>H		7	25		4	NA		1000000
>02163399054	161
>1992	1	26	2		SP0004228	8
>H		7	25		4	NA		1000000
>02163399054	8
>1992	1	25	NA		SP0052652	8
>H		7	25		4	NA		1000000
>02163399057	85
>1992	1	26	NA		SP0037940	8
>H		7	25		4	NA		1000000
>02163399058	70
>1992	1	27	NA		SP0072357	8
>H		7	25		4	NA		1000000
>02163399059	15
>1992	1	27	NA		SP0072357	8
>H		7	25		4	NA		1000000
>02163399059	20
>1992	1	27	NA		SP0026324	8
>H		7	25		4	NA		1000000
>02163399060	8
>1992	1	28	1		SP0072357	8
>H		7	25		4	NA		1000000
>02163399062	200
>
>How can I use unique to extract the rows that have repeated tripid's
>only, not a unique value for each variable but only for TRIPID.  I then
>want to condense the unique values by summing the CONVUNIT for each
>unique value of TRIPID.  I posted a similar question last week and
>received a sufficient answer of how to do this without using uniqe.  The
>solution below worked just fine on this sample data set but the full
>data set has 446,000 rows of data and my computer and R simply cannot
>handle this follwing code on data this large.
>
>conds<-by(Step4,Step4$TRIPID,function(x)
>replace(x[1,],"CONVUNIT",sum(x$CONVUNIT)))
>Step5<-do.call(rbind,conds)
>
>Thank you,
>
>Cameron Guenther, Ph.D.
>Associate Research Scientist
>FWC/FWRI, Marine Fisheries Research
>100 8th Avenue S.E.
>St. Petersburg, FL 33701
>(727)896-8626 Ext. 4305
>cameron.guenther at myfwc.com
>
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