[Rd] colnames is slow for data.frames with implicit row.names

From: Martin Morgan <mtmorgan_at_fhcrc.org>
Date: Wed 27 Sep 2006 - 13:13:56 GMT


colnames on a data.frame with implicit row.names

> df <- data.frame(x=1:6000000)

is slow

> system.time(colnames(df))

[1] 21.655 0.327 21.987 0.000 0.000
> system.time(names(df))

[1] 0 0 0 0 0

because colnames calls dimnames calls row.names.data.frame calls as.character on the implicit row.names.

-- 
Martin T. Morgan
Bioconductor / Computational Biology
http://bioconductor.org

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