[R] drawing ellipses in R

[Greg Snow]

Those formulas are the standard way to convert from polar coordinates to Euclidean coordinates.  The polar coordinates are 'r' which is the radius or distance from the center point and 'theta' which is the angle (0 is pointing in the positive x direction).

If r is constant and theta coveres a full cycle then you will get a circle.

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of mmstat at comcast.net
Sent: Monday, October 31, 2011 10:50 PM
To: r-help at stat.math.ethz.ch
Subject: [R] drawing ellipses in R

Hello, 

I have been following the thread dated Monday, October 9, 2006 when Kamila Naxerova asked a question about plotting elliptical shapes. Can you explain the equations for X and Y. I believe they used the parametric form of x and y (x=r cos(theta), y=r sin(theta). I don't know what r is here ? Can you explain 1)the origin of these equations and 2) what is r? 

Sincerely, 
Mary A. Marion 

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