On Sat, Nov 12, 2011 at 10:50 AM, Yackov Lubarsky <yluba...@gmail.com> wrote: > Hi, > > I would like to plot a x,y curve described by the equation : > > Ax^2 + Bx + Cy^2 + Dy + E == 0 > > (A,B,C,D,E are constants) > > This sounds like quite the common task but haven't been able to figure > out how to do this. Could you please help ? I am new to R so probably > missing something basic.
What you may be missing was all figured out by the ancient Greeks and they didnt even have R in their alphabet! You've got this: http://mathworld.wolfram.com/QuadraticCurve.html but with b=0. I'm not sure how many of the awkward cases (line pairs, imaginary everything) disappear with b=0, but you can compute the Delta, I, J, and K determinants to figure it out. Then set theta to seq(0,2*pi,len=100) and compute r from the polar equation form. Plot r*cos(theta), r*sin(theta)... Confession: its been a long time since I did maths like this (forgive me father, for I have not sin'd). Barry ______________________________________________ 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.