[R] Generalizing call to function

[Berend Hasselman]

. 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)
> 
> Thanks in advance.
> 
> 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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