[R] Help with functions

[Liaw, Andy]

Just remember that you are writing _functions_, not _macros_.  If you want
the function to be able to see an object, pass that object to the function
as one of the arguments.  Alternatively, you can use the lexical scoping in
R and define the (sub)functions inside the `main' function.

Andy

From: Pryseley Assam
> 
> Dear R-users
>    
>   I intend to create a function which calls some smaller 
> other functions in return. Some of these smaller functions 
> all call some functions. I do not know a good way to do this. 
> I tried using the source() function to include the smaller 
> functions within the main functions before they are called. 
> This does not work, or maybe i am not doing the right thing. 
>   For example:
>    
>   the following quantities are computed in the main function 
> (only a part of the main function is shown below)
>    
>     ###############################################################
>   # quantities for bootstrap confidence intervals
>   ###############################################################
>   r.value<- cor(x,y)
>   npb.B <- mean(r)-r.value
>   npb.mean <- mean(r)
>   npb.var <- var(r)
>   r.star <- sort(r)
>   z.star <- (r.star - mean(r.star))/sqrt(var(r.star))
> 
>    
>   after which the main function calls the function 
> (i.s.conf.int) shown below, which is saved in a different script file
>    
>   ################################################### 
>     # Confidence Interval 
>   ###################################################
>   i.s.conf.int <- function(type) {
>   switch(type,
>   a = nci(),
>   b = inci(),
>   c = bbi(),
>   d = pi(),
>   e = si())
>   }
>    
>   Also, this 'sub' function (i.s.conf.int) may call one of 5 
> other smaller functions saved in yet another file, or the 
> same file as the function "i.s.conf.int".
>    
>   However, these 5 functions need the quantities calculated 
> in the main function. One of these functions is shown below:
>    
>   ###############################################################
>   # nonparametric bootstrap normal confidence interval
>   ###############################################################
>   nci <-function () {
>   npb.n.L <- r.value - 1.96*sqrt(npb.var)
>   npb.n.U <- r.value + 1.96*sqrt(npb.var)
>   npb.n <- array(data = c( npb.n.L, npb.n.U), 
>   dim = c(1,2), 
>   dimnames = list("Estimates" ,c("LowerBound","UpperBound")))
>   
>   npb.n.CI <- list( Type = "Normal Confidence Interval",
>   ConfidenceInterval= npb.n)
>   npb.n.CI
>   }
>    
>   I use the source() function to include these 
> "secondary/sub" functions, just before they are called the 
> main function. I get an Error message when any of the 5 small 
> functions is executing : that it can not find the quantities 
> calculated in the main function. 
>    
>   So my question boils down to how can i call functions from 
> different files in the main function, so that the recognise 
> quantities already calculated in the main function or passed 
> as arguements to the main function ?
>    
>   Thanks 
>   Pryseley.
>    
> 
> 
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