[Rd] axis() ignores supplied value of argument mgp[3]?

[Prof Brian Ripley]

On Sun, 3 Aug 2008, J. R. M. Hosking wrote:

> Prof Brian Ripley wrote:
>> What is true is that the line is set before the inline setting of mgp is 
>> processed: it all depends on what 'supplied' means, and you supplied two 
>> values.
>> 
>> This is changed in R-patched now.
>
> Thank you, that works.  Here is a perhaps related issue:
>
> R Help on 'axis' for argument 'line' says "The relative placing of
> tick marks and tick labels is unchanged".  But this appears not to be
> the case when graphics parameter mgp[3] is nonzero:
>
>  plot(1:4, yaxt="n")
>  par(mgp=c(3,2,1))
>  axis(2, 1:2)
>  axis(2, 3:4, line=1)
>
> which one (or, at least, I) would expect to place all the tick labels
> the same distance into the margin, does not in fact do so.

I don't think that is what it says. Setting 'line' or 'pos' temporarily 
sets mgp[3] to zero (which is what the help implies in parts you did not 
quote).

Otherwise 'line' would just duplicate mgp[3].

> My interpretation is that axis() is taking mgp[2] rather than the
> correct mgp[2]-mgp[3] as the relative position of the tick mark with

Why is it correct when you have been told 'mgp[3]' was overridden?
We could explicitly say it is treated as zero for ultimate clarity.

> respect to the axis line.
>
> J. R. M. Hosking
>
>
>> R.version
>               _
> platform       i386-pc-mingw32
> arch           i386
> os             mingw32
> system         i386, mingw32
> status
> major          2
> minor          7.1
> year           2008
> month          06
> day            23
> svn rev        45970
> language       R
> version.string R version 2.7.1 (2008-06-23)
>
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>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595