# Re: [R] writing a simple function

From: <Bill.Venables_at_csiro.au>
Date: Thu, 14 Feb 2008 00:53:56 +1000

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
PO Box 120, Cleveland, 4163
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

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