From: Ted Harding <Ted.Harding_at_nessie.mcc.ac.uk>

Date: Mon 19 Sep 2005 - 19:48:31 EST

E-Mail: (Ted Harding) <Ted.Harding@nessie.mcc.ac.uk> Fax-to-email: +44 (0)870 094 0861

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Sep 21 02:03:43 2005

Date: Mon 19 Sep 2005 - 19:48:31 EST

On 19-Sep-05 Robin Hankin wrote:

*> Hi
**>
**> the manpage for persp() has a wonderful section where a the
**> trans3d() function is used with points() and lines() to add
**> red dots and a green sinusoid to the Mexican hat surface.
**>
**> Does anyone have a way to tell what distance a point is from
**> the eye/camera?
**>
**> Take the following line:
**>
**> lines (trans3d(x, y=10, z= 6 + sin(x), pm = res), col = 3)
**>
**> Is there a function like trans3d() that returns a vector of
**> distances from the x,y,z point to the camera? I want this so
**> I can plot clouds of points with the further ones in smaller
*

> plotsizes, and perhaps even fading to white (as though viewed

> through fog).

Wonderfully put! That's what statistics is about!

xE <- r*sin(theta + pi)*cos(phi) yE <- r*cos(theta + pi)*cos(phi) zE <- r*sin(phi)

2. Centre of box relative to real (0,0,0)

xC <- mean(xlim); yC <-mean(ylim); xC <- mean(zlim)

3. Coordinates of (x,y,z) relative to Eye

x1 <- x - xE - xC; y1 <- y - yE - yC; z1 <- z - zE - zC

4. Distance from Eye to (x,y,z)

(Hoping I've not got anything the wrong way round there!)

Best wishes,

Ted.

E-Mail: (Ted Harding) <Ted.Harding@nessie.mcc.ac.uk> Fax-to-email: +44 (0)870 094 0861

Date: 19-Sep-05 Time: 10:17:55 ------------------------------ XFMail ------------------------------ ______________________________________________R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Wed Sep 21 02:03:43 2005

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