[Rd] Error in documentation for ?legend

peter dalgaard pdalgd at gmail.com
Sat Mar 25 14:10:57 CET 2017

> On 25 Mar 2017, at 00:39 , POLITZER-AHLES, Stephen [CBS] <stephen.politzerahles at polyu.edu.hk> wrote:
> To whom it may concern:
> The help page for ?legend refers to a `title.cex` parameter, which suggests that the function has such a parameter.

No it does not. All arguments are listed and documented, none of them is title.cex, and there's no "...".

However, the documentation for "cex" has this oddity inside:

     cex: character expansion factor *relative* to current
          ‘par("cex")’.  Used for text, and provides the default for
          ‘pt.cex’ and ‘title.cex’.

Checking the sources suggests that this is the last anyone has seen of title.cex:

pd$ grep -r title.cex src
src/library/graphics/man/legend.Rd:    \code{pt.cex} and \code{title.cex}.}

The text was inserted as part of the addition of the title.col (!) argument, so it looks like the author got some wires crossed.


> As far as I can tell, though, it doesn't; here's an example:
>> plot(1,1)
>> legend("topright",pch=1, legend="something", title="my legend", title.cex=2)
> Error in legend("topright", pch = 1, legend = "something", title = "my legend",  :
>  unused argument (title.cex = 2)
> This issue appears to have been discussed online before (e.g. here's a post from 2011 mentioning it: http://r.789695.n4.nabble.com/Change-the-text-size-of-the-title-in-a-legend-of-a-R-plot-td3482880.html) but I'm not sure if anyone ever reported it to R developers.
> Is it possible for someone to update the ?legend documentation page so that it doens't refer to a parameter that isn't usable?
> Best,
> Steve Politzer-Ahles
> ---
> Stephen Politzer-Ahles
> The Hong Kong Polytechnic University
> Department of Chinese and Bilingual Studies
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Peter Dalgaard, Professor,
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