Re: [R] problem using uniroot with integrate

From: Sundar Dorai-Raj <sundar.dorai-raj_at_pdf.com>
Date: Thu 10 Mar 2005 - 04:57:33 EST

Ken Knoblauch wrote on 3/9/2005 10:27 AM:
> Hi,
>
> I'm trying to calculate the value of the variable, dp, below, in the
> argument to the integral of dnorm(x-dp) * pnorm(x)^(m-1). This
> corresponds to the estimate of the sensitivity of an observer in an
> m-alternative forced choice experiment, given the probability of
> a correct response, Pc, a Gaussian assumption for the noise and
> no bias. The function that I wrote below gives me an error:
>
> Error in f(x, ...) : recursive default argument reference
>
> The problem seems to be at the statement using uniroot,
> because the furntion est.dp works fine outside of the main function.
> I've been using R for awhile but there are still many nuances
> about the scoping and the use of environments that I'm weak on
> and would like to understand better. I would appreciate any
> suggestions or solutions that anyone might offer for fixing
> my error. Thank you.
>
> dprime.mAFC <- function(Pc, m) {
> est.dp <- function(dp, Pc = Pc, m = m) {
>
> pr <- function(x, dpt = dp, m0 = m) {
> dnorm(x - dpt) * pnorm(x)^(m0 - 1)
> }
>
> Pc - integrate(pr, lower = -Inf, upper = Inf,
> dpt = dp, m0 = m)$value
> }
>
> dp.res <- uniroot(est.dp, interval = c(0,5), Pc = Pc, m = m)
> dp.res$root
> }
>

Ken,

Look at the argument list for ?uniroot and think "partial matching". You're "m" is being interpretted for "maxiter". Simply change to

dp.res <- uniroot(est.dp, interval = c(0,5), Pc = Pc, m0 = m)

and in other places for consistency and the error goes away. Of course, since you gave no working example, I'm not sure if other errors are present that I'm missing.

--sundar



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