Re: [Rd] Problems with plot and Quartz device / What is alpha?

From: Thomas Richardson <thomasr_at_u.washington.edu>
Date: Wed, 03 Jun 2009 12:00:35 -0700 (PDT)

PS Please forgive my ignorance, but when you say:

> BTW: you may want to use something like pch=19, cex=0.1 (and maybe add some
> alpha to get a quick density estimation).

I don't know what alpha refers to here.

Thanks again.

Best wishes,

Thomas

>
> Cheers,
> S
>
>
>> So I guess it might be related to the
>> "special treatment" of "." described on help(points) ??
>> ---
>> Value pch="." (equivalently pch = 46) is handled specially. It is a
>> rectangle of
>> side 0.01 inch (scaled by cex).
>> ---
>>
>> I find this behaviour unnerving: the (resized) plots made it look as if
>> there
>> was a lot of structure in the data, but on closer inspection it turned out
>> to be
>> entirely a consequence of the quartz device and plot function!
>>
>> I can't imagine that this behaviour is intended - even if it were intended
>> to
>> suppress points (like some axis labels) - it seems strange that enlarging
>> the
>> window makes points disappear. (I also tried setting dpi=72 in quartz(),
>> but
>> this did not fix the problem).
>>
>> Thanks in advance.
>>
>> Thomas
>>
>> ------------------------------------------------------
>> sessionInfo()
>> R version 2.9.0 (2009-04-17)
>> i386-apple-darwin8.11.1
>>
>> locale:
>> en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8
>>
>> attached base packages:
>> [1] stats graphics grDevices utils datasets methods base
>>
>> ______________________________________________
>> R-devel_at_r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>
>>
>



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