# [R] Generalizing call to function

Berend Hasselman bhh at xs4all.nl
Wed Sep 7 18:54:21 CEST 2011

```. wrote:
>
> Hello guys,
>
> I would like to ask for help to understand what is going on in
> "func2". My plan is to generalize "func1", so that are expected same
> results in "func2" as in "func1". Executing "func1" returns...
>
> 0.25 with absolute error < 8.4e-05
>
> But for "func2" I get...
>
> Error in dpois(1, 0.1, 23.3065168689948, 0.000429064542600244,
> 3.82988398013855,  :
>  unused argument(s) (0.000429064542600244, 3.82988398013855,
> 0.00261104515224461, 1.37999516465199, 0.0072464022020844,
> 0.673787740945863, 0.0148414691931943, 0.383193602946711,
> 0.0260964690514175, 0.236612585866545, 0.0422631787036055,
> 0.152456705113438, 0.0655923922306948)
>
>
> func1 <- function(y, a, rate) {
>        f1 <- function(n, y, a, rate) {
>                lambda <- a * n
>                dexp(n, rate) * dpois(y, lambda)
>        }
>        integrate(f1, 0, Inf, y, a, rate)
> }
>
> func1(1, 0.1, 0.1)
>
>
> func2 <- function(y, a, rate, samp) {
>        f1 <- function(n, y, a, rate, samp) {
>
>                SampDist <- function(y, a, n, samp) {
>                        lambda <- a * n
>                        dcom <- paste("d", samp, sep="")
>                        dots <- as.list(c(y, lambda))
>                        do.call(dcom, dots)
>                }
>
>                dexp(n, rate) * SampDist(y, a, n, samp)
>        }
>        integrate(f1, 0, Inf, y, a, rate, samp)
> }
>
> func2(1, 0.1, 0.1, "pois")
>

You need to replace the line with "dots <- as.list(c(y, lambda))" with this

dots <- list(y, lambda)

You could also replace the two lines

dots <- as.list(c(y, lambda))
do.call(dcom, dots)

with the single line

do.call(dcom, list(y, lambda))

See the description of the argument "args" of do.call.

You should now get the same answer as for func1.
Deciding if this is correct is up to you.

Berend

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