[R] [FORGED] Re: draw stripes in a circle in R

[jeanphilippe.fontaine]

Envoyé depuis mon appareil Samsung

-------- Message d'origine --------
De : Rolf Turner <r.turner at auckland.ac.nz> 
Date : 14/06/2017  22:53  (GMT+01:00) 
À : David Winsemius <dwinsemius at comcast.net> 
Cc : r-help at r-project.org 
Objet : Re: [R] [FORGED] Re:  draw stripes in a circle in R 

On 15/06/17 05:29, David Winsemius wrote:
> 
>> On Jun 14, 2017, at 10:18 AM, David Winsemius <dwinsemius at comcast.net> wrote:
>>
>>
>>> On Jun 14, 2017, at 9:46 AM, Jeff Newmiller <jdnewmil at dcn.davis.ca.us> wrote:
>>>
>>> I don't see a question. If your question is whether R supports pattern fills, AFAIK it does not. If that is not your question, ask one.
>>> -- 
>>> Sent from my phone. Please excuse my brevity.
>>>
>>> On June 14, 2017 7:57:41 AM PDT, jean-philippe <jeanphilippe.fontaine at gssi.infn.it> wrote:
>>>> dear R users,
>>>>
>>>> I would like to fill a circle with yellow stripes instead of a uniform
>>>> yellow color. To draw the circle I used the following command after
>>>> having loaded the (very nice !) plotrix library :
> 
> I finally understood the question and it needs a hack to the draw.circle function in plotrix since the angle and density arguments don't get passed in:
> 
> First get code for draw.circle:
> 
> ------
> 
> draw.circle   # then copy to console and edit
> 
> draw.circle2  <- function (x, y, radius, nv = 100, border = NULL, col = NA, lty = 1,
>                             density=NA, angle=45,  lwd = 1 )
> {
>      xylim <- par("usr")
>      plotdim <- par("pin")
>      ymult <- getYmult()
>      angle.inc <- 2 * pi/nv
>      angles <- seq(0, 2 * pi - angle.inc, by = angle.inc)
>      if (length(col) < length(radius))
>          col <- rep(col, length.out = length(radius))
>      for (circle in 1:length(radius)) {
>          xv <- cos(angles) * radius[circle] + x
>          yv <- sin(angles) * radius[circle] * ymult + y
>          polygon(xv, yv, border = border, col = col, lty = lty, density=density, angle=angle,
>                  lwd = lwd)
>      }
>      invisible(list(x = xv, y = yv))
> }
> 
> Now run your call to pdf with draw.circle2 instead of draw.circle.

This is just idle curiosity, since I'm not really able to contribute 
anything useful, but I can't resist asking:  When I try to run the OP's 
code I get an error:

> Error in alpha("red", 0.4) : could not find function "alpha".

Sorry for the lack of precision, alpha is just to add some transparency to the color. This alpha parameter ranges from 0 fully transparent to 1, full color.I don't remember having loaded any package to use this function, I think it is there in base R.
Why does this (apparently) not happen to anyone else?  Why does the 
universe pick on *me*?  What is the function "alpha()"?  Where is it to 
be found?

Searching on "alpha" is of course completely unproductive; there are far 
too many (totally irrelevant) instances.

cheers,

Rolf

-- 
Technical Editor ANZJS
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276

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