R: Quadratic curve is printing as dozens of lines

Question

Instead of printing a nice curve, R is printing a dense mess of line segments. The edge of that dense mess looks exactly like the curve I\'m trying to print, though.

Answer 1

lines will draw lines between the points in the order they are given. Something like

plot(X2,Y2)
ox2 <- order(X2)
lines(X2[ox2],fitted(model2s)[ox2])

should give you what you're looking for.