I was meaning something like the following:
x <- seq(.2, .3, by = .01)
f <- function(x){
x*cos(x)-2*x**2+3*x-1
}
plot(x,f(x), type = "l")
abline(h = -.1)
But I'm guessing "uniroot" will do this?---I haven't looked far into the
uniroot function to see if it will solve this.
On Aug 12, 2010, at 1:00 PM, David Winsemius wrote:
On Aug 12, 2010, at 3:54 PM, TGS wrote:
> Actually I spoke too soon David.
>
> I'm looking for a function that will either tell me which point is the
> intersection so that I'd be able to plot a point there.
>
> Or, if I have to solve for the roots in the ways which were demonstrated
> yesterday, then would I be able to specify what the horizontal line is, for
> instance in the case where y (is-not) 0?
Isn't the abline h=0 represented mathematically by the equation y=0 and
therefore you are solving just for the zeros of "f" (whaich are the same as for
(f-0)? If it were something more interesting, like solving the intersection of
two polynomials, you would be solving for the zeros of the difference of the
equations. Or maybe I have not understood what you were requesting?
>
> On Aug 12, 2010, at 12:47 PM, David Winsemius wrote:
>
>
> On Aug 12, 2010, at 3:43 PM, TGS wrote:
>
>> I'd like to plot a point at the intersection of these two curves. Thanks
>>
>> x <- seq(.2, .3, by = .01)
>> f <- function(x){
>> x*cos(x)-2*x**2+3*x-1
>> }
>>
>> plot(x,f(x), type = "l")
>> abline(h = 0)
>
> Would this just be the uniroot strategy applied to "f"? You then plot the x
> and y values with points()
>
>
David Winsemius, MD
West Hartford, CT
______________________________________________
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.
