[R] writing a simple function

[Bill.Venables at csiro.au]

Your code looks like matlab, but I don't see how it would work even
there.

The specific problem is the to refer to an array, you do so with square
brackets [..] and not round ones, (though your v is not an array,
anyway, so your troubles are just starting).

Let's tackle what I think may be your problem directly.  You say you
want to know if the interval (a,b) overlaps (c,d) or not.

OK, suppose a, b, c and d are four vectors defining intervals
(a[i],b[i]) and (c[i],d[i]), and you want a vector of logicals as the
result.  Here is a suggestion.

overlap <- function(a, b, c, d) 
	!((pmax(a, b) < pmin(c, d)) | (pmax(c, d) < pmin(a, b)))

Here is a little demo

> set.seed(2008)
> w <- runif(10)
> x <- runif(10)
> y <- runif(10)
> z <- runif(10)
> o <- overlap(w, x, y, z)
> data.frame(a=w, b=x, c=y, d=z, o)
           a          b          c         d     o
1  0.5711326 0.32063318 0.02002140 0.3581223  TRUE
2  0.6422710 0.09871573 0.02017792 0.6659485  TRUE
3  0.4645480 0.38348609 0.57137732 0.5682764 FALSE
4  0.8695450 0.99505570 0.78598674 0.8700771  TRUE
5  0.6338629 0.62817830 0.03717119 0.6008403 FALSE
6  0.3897689 0.34575269 0.70860446 0.7215733 FALSE
7  0.5236651 0.91862887 0.27005734 0.6000776  TRUE
8  0.7730075 0.02215747 0.76042526 0.9626952  TRUE
9  0.6267855 0.64686826 0.81222122 0.6340692  TRUE
10 0.1752022 0.66873049 0.58638984 0.1629897  TRUE
> 




Bill Venables
CSIRO Laboratories
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-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of mohamed nur anisah
Sent: Thursday, 14 February 2008 12:22 AM
To: r-help at r-project.org
Subject: [R] writing a simple function

Dear lists,
   
  any suggestion on how to write a function to return a TRUE if interval
[a,b] overlaps the interval [c,d]. I've tried it but an error occur
saying that 'could not find function v ; in addition warning message
occur'. Below is my codes.Please help me sort this problem as i'm in
process of learning of writing a function. Many thanks
   
  overlap<-function(m,n){
t=length(m)
v=length(n)
tt=logical(t)
tv=logical(v)
 for(i in 1:m){
  for(i in 1:n){
  if(v(i,j)<=t(i,j)){
     tt=T
     tv=T
   }
  }
 }
k=c(tt,tv)
return(k)
}
   
  Regards,
  Anisah

       
---------------------------------

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