[Rd] minor flaw in integrate()

[Gabor Grothendieck]

If integrate is changed it would be nice at the same time to make it
into an S3 generic.  deriv already is an S3 generic but strangely integrate
is not.  Ryacas provides a deriv method but for integrate Ryacas inconsistently
provides Integrate since integrate is not generic.

On 6/28/07, Peter Ruckdeschel <Peter.Ruckdeschel at uni-bayreuth.de> wrote:
> Hi,
>
> I noticed a minor flaw in integrate() from package stats:
>
> Taking up arguments lower and upper from integrate(),
>
>   if (lower ==  Inf) && (upper ==  Inf)
>
>       or
>
>   if (lower == -Inf) && (upper == -Inf)
>
> integrate() calculates the value for (lower==-Inf) && (upper==Inf).
>
> Rather, it should return 0.
>
> Quick fix:
>
> ### old code ###
> ### [snip]
>    else {
>            if (is.na(lower) || is.na(upper))
>                stop("a limit is missing")
>            if (is.finite(lower)) {
>                inf <- 1
>                bound <- lower
>            }
>            else if (is.finite(upper)) {
>                inf <- -1
>                bound <- upper
>            }
>            else {
>                inf <- 2
>                bound <- 0
>            }
>            wk <- .External("call_dqagi", ff, rho = environment(),
>                as.double(bound), as.integer(inf), as.double(abs.tol),
>                as.double(rel.tol), limit = limit, PACKAGE = "base")
>    }
> ### [snip]
>
> ### new code  to replace the old one ###
>
> ### [snip]
>    else {
>            if (is.na(lower) || is.na(upper))
>                stop("a limit is missing")
>
>            if (lower == upper){
>
>                wk <- list("value" = 0, "abs.error" = 0,
>                        "subdivisions" = subdivisions,
>                        "ierr" = 0 )
>
>            } else {
>                    if (is.finite(lower)) {
>                        inf <- 1
>                        bound <- lower
>                    }
>                    else if (is.finite(upper)) {
>                            inf <- -1
>                        bound <- upper
>                    }
>                    else {
>                        inf <- 2
>                        bound <- 0
>                    }
>                    wk <- .External("call_dqagi", ff, rho = environment(),
>                            as.double(bound), as.integer(inf),
>                            as.double(abs.tol), as.double(rel.tol),
>                            limit = limit, PACKAGE = "base")
>
>            }
>    }
> ### [snip]
>
> Best, Peter
>
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