[R] arrows and points for error bars

[Simon Pickett]

Hi there,
I did what Peter Dalgaard very kindly suggested and saved it as a pdf and
viewed it using adobe, which as if by magic resolves the problem. It must
have been a pixel issue with the r graphics device.
Sorry to have wasted your time, thanks for your help, always appreciated.
Simon.


> It would be very helpful to have a reproducible example, including the OS
> and graphics device used.
>
> For example, this may only happen with certain values of 'pch' -- e.g.
> some graphics devices (pdf is one) plot circles using completely different
> code from squares.  And we frequently see reports of problems with R
> graphics where the bug is in the viewer software or the including
> application (Word being notorious for mis-rendering WMF files).
>
>
> On Fri, 20 Oct 2006, Peter Dalgaard wrote:
>
>> "Simon Pickett" <S.Pickett at exeter.ac.uk> writes:
>>
>>> Hello everyone,
>>> I have successfully made an error bar graph using the points() command
>>> with the arrows() command to maually add on the standard errors.
>>>
>>> However, one slightly annoying feature of using this method is that the
>>> points dont line up exactly with the arrows (if you look carefully the
>>> points are never perfectly in the centre of the arrow), even when you
>>> move
>>> the arrows around in an attempt to correct this.
>>
>> Is this a pixelization issue? If the line is an odd number of pixels
>> wide and the point is an even number of pixels across, then there is
>> just no way to line them up. It should go away with increased
>> resolution, e.g. when plotting to pdf() and printing on a laser
>> printer.
>>
>>> Secondly I cant seem to force the points to appear on top of the arrows
>>> i.e. with the arrows behind the points. Uing ADD=TRUE to either command
>>> wont work.
>>
>> Plot the points last and use a filled symbol, or pch %in% 21:25 with
>> bg="white". (example(points) is generally helpful in these matters)
>>
>>> Does anyone have any solutions to this problem, or maybe even a
>>> different
>>> way of making error plots?
>>>
>>> Sorry if this seems a bit pedantic, but it would be great if I could
>>> resolve this problem and so enable me to use R for publication standard
>>> graphs...
>>>
>>> Thanks everyone :-)
>>
>>
>>
>>
>
> --
> 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
>


Simon Pickett
PhD student
Centre For Ecology and Conservation
Tremough Campus
University of Exeter in Cornwall
TR109EZ
Tel 01326371852