[R] How to plot a Quadratic Model?

[Kingsford Jones]

see ?curve

e.g.

qftn <- function(x) 1 + 2*x - .1*x^2
curve(qftn, 0, 10)

hth,

Kingsford

On Mon, Oct 5, 2009 at 9:42 AM, Juliano van Melis <jvmelis at gmail.com> wrote:
> Good day for all,
>
> I'm a beginner aRgonaut, thus I'm having a problem to plot a quadratic model
> of regression in a plot.
> First I wrote:
>
>>plot(Y~X)
>
> and then I tried:
>
>>abline(lm(Y~X+I(X^2))
>
> but "abline" only uses the first two of three regression coefficients, thus
> I tried:
>
>>line(lm(Y~X+I(X^2))
>
> but a message error is showed ("insufficient observations").
>
> Therefore, I want to know: how could I plot a quadratic line in my plot
> graph?
>
> thanks!
>
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>
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