On 11-11-12 5:50 AM, Yackov Lubarsky 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.
R is not very good at that, but one way to do it is to draw a contour
plot of the bivariate function, with a single contour at level 0. For
example,
A <- B <- C <- D <- 1
E <- -1
x <- y <- seq(-3, 3, len=100)
z <- outer(x, y, function(x, y) A*x^2 + B*x + C*y^2 + D*y + E)
contour(x, y, z, levels=0, drawLabels=FALSE)
Another would be to solve for y as a function of x, and draw both
branches.
Duncan Murdoch
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