[R] Odp: aggregating strings

[Petr PIKAL]

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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