R help - Oct 2007 - reason for error in small function?

Running the function below, tested using the cardiff dataset from
splancs generates the following error.   What changes do I need to
make to get the function to work?  Thanks.  --Dale
> gen.rpoints(events, poly, 99)
> rpoints
Error: object "rpoints" not found

# test spatial data
library(splancs)
data(cardiff)
attach(cardiff)
str(cardiff)
events <- as.points(x,y)

### non-working function ####

gen.rpoints <- function(events, poly, nsim){
rpoints <- array(0, dim=c(nrow(events),2,nsim))
  for (i in 1:nsim) {
    rpoints[, ,i] <- csr(poly, nrow(events))
  }
}

On 10/11/2007 2:17 PM, Dale Steele wrote:
> Running the function below, tested using the cardiff dataset from
> splancs generates the following error.   What changes do I need to
> make to get the function to work?  Thanks.  --Dale
> 
>> gen.rpoints(events, poly, 99)
>> rpoints
> Error: object "rpoints" not found
> 
> # test spatial data
> library(splancs)
> data(cardiff)
> attach(cardiff)
> str(cardiff)
> events <- as.points(x,y)
> 
> ### non-working function ####
> 
> gen.rpoints <- function(events, poly, nsim){
> rpoints <- array(0, dim=c(nrow(events),2,nsim))
>   for (i in 1:nsim) {
>     rpoints[, ,i] <- csr(poly, nrow(events))
>   }
> }
You generate rpoints within the scope of the function, but you don't 
return it.  Change your function to

gen.rpoints <- function(events, poly, nsim){
   rpoints <- array(0, dim=c(nrow(events),2,nsim))
   for (i in 1:nsim) {
     rpoints[, ,i] <- csr(poly, nrow(events))
   }
   rpoints
}

and call it as

rpoints <- gen.rpoints(...)

(There are ways to create variables outside of the scope of the 
function, but you shouldn't use them.)

Duncan Murdoch

You need to return the value from the function.  "rpoints" is local to
the function and not visible.

gen.rpoints <- function(events, poly, nsim){
rpoints <- array(0, dim=c(nrow(events),2,nsim))
 for (i in 1:nsim) {
   rpoints[, ,i] <- csr(poly, nrow(events))
 }
 rpoints
}

rpoints <- gen.rpoints(events, poly, 99)


On 10/11/07, Dale Steele <dale.w.steele at gmail.com>
wrote:
> Running the function below, tested using the cardiff dataset from
> splancs generates the following error.   What changes do I need to
> make to get the function to work?  Thanks.  --Dale
>
> > gen.rpoints(events, poly, 99)
> > rpoints
> Error: object "rpoints" not found
>
> # test spatial data
> library(splancs)
> data(cardiff)
> attach(cardiff)
> str(cardiff)
> events <- as.points(x,y)
>
> ### non-working function ####
>
> gen.rpoints <- function(events, poly, nsim){
> rpoints <- array(0, dim=c(nrow(events),2,nsim))
>  for (i in 1:nsim) {
>    rpoints[, ,i] <- csr(poly, nrow(events))
>  }
> }
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?

On Thu, Oct 11, 2007 at 02:17:14PM -0400, Dale Steele
wrote:
> Running the function below, tested using the cardiff dataset from
> splancs generates the following error.   What changes do I need to
> make to get the function to work?  Thanks.  --Dale
> 
> > gen.rpoints(events, poly, 99)
> > rpoints
> Error: object "rpoints" not found
Looks like the variable rpoints does not exist.
> gen.rpoints <- function(events, poly, nsim){
> rpoints <- array(0, dim=c(nrow(events),2,nsim))
>   for (i in 1:nsim) {
>     rpoints[, ,i] <- csr(poly, nrow(events))
>   }
> }
OK ? so I guess this function is intended to create the variable
rpoints. And it does ? but the variable exists only inside the function.
You could fix this by using the <<- operator but it is much cleaner to add
return(rppoints) as the last line of your function and then call it like
this:

rppoints <- gen.rpoints(events, poly, 99)

cu
	Philipp

-- 
Dr. Philipp Pagel                              Tel.  +49-8161-71 2131
Lehrstuhl f?r Genomorientierte Bioinformatik   Fax.  +49-8161-71 2186
Technische Universit?t M?nchen
Wissenschaftszentrum Weihenstephan
85350 Freising, Germany

 and

Institut f?r Bioinformatik / MIPS
GSF - Forschungszentrum f?r Umwelt und Gesundheit
Ingolst?dter Landstrasse 1
85764 Neuherberg, Germany
http://mips.gsf.de/staff/pagel