> I need to find the root of the second derivative of many curves and do not
> want to cut and paste the expression results from the deriv() or D()
> functions every time. Below is an example. What I need to do is refer to
> "fn2nd" in the uniroot() function, but when I try something like
> uniroot(fn2nd,c(0,1)) I get an error, so I have resorted to pasting in the
> expression, but this is highly inefficient.
>
> Thanks, J
>
> [...]
What is so wrong with using
r <- uniroot(function(x) eval(fn2nd, list(x=x)),
interval=c(0, 1), tol=0.0001)
(I thought you were almost there) or even
fn2nd_fun <- function(x) eval(fn2nd, list(x=x))
ex <- seq(from=0, to=1, length.out = 1000)
y1 <- fn2nd_fun(ex)
...
r <- uniroot(fn2nd_fun, interval=c(0, 1), tol=0.0001)
--Hans Werner
> r$root
> abline(h=0, col = "red")
> abline(v=r$root, col = "green")
> arrows(0.6, -2, r$root,0, length = 0.1, angle = 30, code = 2, col = "red")
> text(0.765,-2.3,paste("b = ",r$root,sep=""))
>
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