R help - Feb 2008 - 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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Hi,
mohamed nur anisah wrote:
> 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

does this do what you want?

overlap <- function(a,b,c,d) {
	all(c:d %in% a:b)
}
overlap(1,5,3,4)
overlap(1,2,3,4)


Best,
Roland

>    
>   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
> 
>        
> ---------------------------------
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> 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.
>

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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AUSTRALIA
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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

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

	[[alternative HTML version deleted]]

______________________________________________
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.

Roland Rau <roland.rproject <at> gmail.com> writes:
> 
> does this do what you want?
> 
> overlap <- function(a,b,c,d) {
> 	all(c:d %in% a:b)
> }
> overlap(1,5,3,4)
> overlap(1,2,3,4)
  Do you really want this to be discrete?  How about

overlap <- function(a,b,c,d) {
   a<c && b>d
}

(although this assumes that a<b and c<d ...)

Hi,

Ben Bolker wrote:
> Roland Rau <roland.rproject <at> gmail.com> writes:
> 
>> does this do what you want?
>>
>> overlap <- function(a,b,c,d) {
>> 	all(c:d %in% a:b)
>> }
>> overlap(1,5,3,4)
>> overlap(1,2,3,4)
> 
>   Do you really want this to be discrete?  How about
> 
> overlap <- function(a,b,c,d) {
>    a<c && b>d
> }
you are absolutely right.[1]
I assume with discrete you mean integers?
I think the bigger problem with my function is that it makes way too 
many comparisons than are actually necessary (memory and time problems).

What about the following function:
overlap <- function(intval1, intval2) {
   (min(intval1) < min(intval2)) && (max(intval1) > max(intval2))
}

Best,
Roland

[1] I realized the problems with my solution almost as soon as I sent 
the email. But I was on a way to a meeting and there was no more time to 
correct it at that moment.