Thanks. It works.
2008/3/1, Greg Snow <[EMAIL PROTECTED]>:
>
> Look at the cnvrt.coords function in the TeachingDemos package.
>
> You should be able to use that function to transform from user
> coordinates to device coordinates (where 0 is left/bottom and 1 is
> right/top), then multiply the device coordinates by the resolution to
> get the pixel numbers.
>
> Hope this helps,
>
> --
> Gregory (Greg) L. Snow Ph.D.
> Statistical Data Center
> Intermountain Healthcare
> [EMAIL PROTECTED]
> (801) 408-8111
>
>
>
> > -----Original Message-----
> > From: [EMAIL PROTECTED]
> > [mailto:[EMAIL PROTECTED] On Behalf Of Guohui Ding
> > Sent: Friday, February 29, 2008 12:12 AM
> > To: R help (E-mail)
> > Subject: [R] How to convert the "user coordinate system" in R
> > graph to"normal coordinate system" whose origin is the
> > upper-leftcornner of the drawing area?
> >
> > Dear friends,
> >
> > The user coordiante system in the R graphics is easy to
> > understand as it simply corresponds to the range of values on
> > the axes of the plot.
> > However, sometimes, we want to kown the coordinates of a
> > region in other system, e.g., the normal coordinate system
> > whose origin is the the upper-left cornner of the drawing
> > area which is used to set the hot regions in the HTML image
> > maps. Is there any suggestion?
> >
> > For example, I execute the code,
> >
> > > png("x.png", width = 480, height = 480,
> > + pointsize = 12, bg = "white", res = 100);
> > > plot(0, xlim=c(0, 100), ylim = c(0,100), type="n") rect(0, 0, 100,
> > > 100) points(0, 0, col = 'red')
> > > dev.off()
> >
> > I will get a figure named "x.png". The resolution of this
> > figure is 100 dpi and the width and height are 480 pixels
> > when I opened it with Photoshop.
> > When I move the cursor to the point drawed by points(0, 0,
> > col = 'red'), I can find the position of this point is about
> > (87, 376) [(x, y)]. I want to know how to convert the (0, 0)
> > in the user coordinate system to this value?
> >
> > I look forward to hearing from you.
> >
> > --
> > ADDRESS: Bioinformatics Center, Shanghai Institutes for
> > Biological Sciences, Chinese Academy of Sciences 320 Yueyang
> > Road, Shanghai 200031, P.R.China
> > TELEPHONE: 86-21-54920086
> >
> > [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@r-project.org mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
>
--
ADDRESS: Bioinformatics Center, Shanghai Institutes for Biological Sciences,
Chinese Academy of Sciences
320 Yueyang Road, Shanghai 200031, P.R.China
TELEPHONE: 86-21-54920086
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