R help - Jul 2009 - aggregating strings

I am currently summarising a data set by collapsing data based on common
identifiers in a column.  I am using the 'aggregate' function to
summarise numeric columns, i.e. "aggregate(dat[,3], list(dat$gene),
mean)".  I also wish to summarise text columns e.g. by concatenating values
in a comma separated list, but the aggregate function can only return scalar
values and so something like "aggregate(dat[,3], list(dat$gene), cat)"
will not work.  Is there a simple function like aggregate that works for strings
in R?

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Hi
r-help-bounces at r-project.org napsal dne 28.07.2009 17:34:35:
> I am currently summarising a data set by collapsing data based on common 
> identifiers in a column.  I am using the 'aggregate' function to 
summarise 
> numeric columns, i.e. "aggregate(dat[,3], list(dat$gene), mean)".
I
also wish
> to summarise text columns e.g. by concatenating values in a comma 
separated 
> list, but the aggregate function can only return scalar values and so 
> something like "aggregate(dat[,3], list(dat$gene), cat)" will not
work.
Is 
> there a simple function like aggregate that works for strings in R?
Try

aggregate(dat[,3], list(dat$gene), paste, collapse=",")

Regards
Petr
> 
> 
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> AstraZeneca UK Limited is a company incorporated in 
Engl...{{dropped:21}}
> 
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http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

You are probably going to get tons of answers, as there are many ways -- and
packages -- to do this (e.g. see packages reshape and plyr). However, you
might want to take a look at ?tapply, for which aggregate() is a wrapper,
for the basic core R approach.

Bert Gunter
Genentech Nonclinical Biostatistics

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
Behalf Of Dry, Jonathan R
Sent: Tuesday, July 28, 2009 8:35 AM
To: r-help at r-project.org
Subject: [R] aggregating strings

I am currently summarising a data set by collapsing data based on common
identifiers in a column.  I am using the 'aggregate' function to
summarise
numeric columns, i.e. "aggregate(dat[,3], list(dat$gene), mean)".  I
also
wish to summarise text columns e.g. by concatenating values in a comma
separated list, but the aggregate function can only return scalar values and
so something like "aggregate(dat[,3], list(dat$gene), cat)" will not
work.
Is there a simple function like aggregate that works for strings in R?

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AstraZeneca UK Limited is a company incorporated in Engl...{{dropped:8}}