[R-sig-eco] altitudinal overlap
Karla Shikev
karlashikev at gmail.com
Wed Jul 15 01:37:28 CEST 2015
Ok, here's another (a bit more challenging) question.
Imagine that I have a S species and a S x 2 matrix of altitudinal limits
(min and max elevation). How would you compute the number of co-occurring
species for each of the S species?
Thanks again for your assistance.
Karla
On Tue, Jul 14, 2015 at 5:14 AM, Stefano Leonardi <stefano.leonardi at unipr.it
> wrote:
>
> The first think that came to my mind:
>
> overlap <- function(v1,v2) {
> ov <-min(max(v1), max(v2)) - max(min(v1), min(v2))
> ifelse(ov > 0, ov, 0)
> }
>
> overlap(dat[1,], dat[2,])
> [1] 0.5
>
>
> Ciao
> Stefano
>
> On 14/07/2015 01:03, Karla Shikev wrote:
>
>> Hi there,
>>
>> This is a newbie question, and I'm sure there are simple ways to do this,
>> but I've spent my entire afternoon and I couldn't get it to work.
>>
>> Imagine that I got the altitudinal range of different species. For
>> instance:
>>
>> dat<-matrix(c(1,3,2.5,4), ncol=2, byrow=TRUE)
>>> dat
>>>
>> [,1] [,2]
>> [1,] 1.0 3
>> [2,] 2.5 4
>>
>>
>> The first line indicates that this species is found between 1 and 3,
>> whereas the second species was found between 2.5 and 4.
>>
>> I need a simple way to calculate the overlap of their extents (0.5 in this
>> case). This way should provide 0 if there is no overlap, and it should
>> also
>> work in the case where one subject is found only within the extent of the
>> second subject.
>>
>> Any help will be greatly appreciated.
>>
>> Karla--
>>
> ======================================================================
> Stefano Leonardi
> Dipartimento di Bioscienze
> Universita` di Parma
> Viale Usberti 11a Phone : +39-0521-905659
> 43124 PARMA (Italy) Fax : +39-0521-905402
>
> Il mio photoblog: http://stefanoleonardi.wordpress.com
> ======================================================================
>
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