Hello,

in adddtition to what Alex points, I would also recomend function K1K2 
in the package ecespa: it implements differences of uivariate and 
bivariate Ripley's K-functions (based on spatstat) to test for 
aggregation and segregation of point patterns in the way suggested by 
Dixon (2002, Ripley's K function. In /The encyclopedia of environmetrics/).
Additionaly, you can use also  the package dixon, which implements  
Dixon's meassure of spatial segregation( Dixon, P.M. 2002. 
Nearest-neighbor contingency table analysis of spatial segregation for 
several species. /Ecoscience/, *9*: 142-151).

HTH,

Marcelino


El 10/03/2013 15:02, Alexandre Villers escribió:
> Hello,
>
> This looks like a job for point pattern statistics. Have a look at the
> spatstat package and the related docs. There are functions (pcfcross
> e.g.) to compare the spatial distribution of marked point patterns (in
> your case the marks will be species name).
> Make sure that point pattern models can be applied to your data set
> first (and check whether you need to account for environmental
> heterogeneity, i.e. first order processes).
>
> HTH
>
> Alex
>
> P.S.: you can find a handy tutorials on the web at www.spatstat.org ...
>
>
>
> On 10/03/2013 15:24, Ross Ahmed wrote:
>> The code below shows a sample of point locations of Brent Goose on mudflats.
>> The black points are the subspecies Dark-bellied Brent Goose, and white
>> points the subspecies Light-bellied Brent Goose:
>>
>> geese <- data.frame(lightLat=c(55.66735, 55.66735, 55.67341, 55.66735,
>> 55.66735),
>>              lightLong=c(-1.833845,-1.833844,-1.833843,-1.833841,-1.833840),
>>              darkLat=c(55.66735,55.66735,55.66735,55.66735,55.61628),
>>              darkLong=c(-1.833851,-1.833851,-1.833848,-1.833850,-1.833849))
>>
>> library(ggplot2)
>> ggplot(geese, aes(lightLong, lightLat)) + geom_point(size=5, color='white')
>> +
>>     geom_point(data=data.frame(geese), aes(darkLong, darkLat), color='black',
>> size=5) +
>>     xlab('long') +
>>     ylab('lat')
>>
>> The two subspecies segregate, as can be seen. I¹m looking for a statistical
>> measure of segregation? Can anyone suggest a suitable measure?
>>
>> Thanks
>> Ross
>>
>>
>>
>>
>> 	[[alternative HTML version deleted]]
>>
>>
>>
>> _______________________________________________
>> R-sig-ecology mailing list
>> R-sig-ecology@r-project.org
>> https://stat.ethz.ch/mailman/listinfo/r-sig-ecology
>
>
> _______________________________________________
> R-sig-ecology mailing list
> R-sig-ecology@r-project.org
> https://stat.ethz.ch/mailman/listinfo/r-sig-ecology


-- 
Marcelino de la Cruz Rot
Depto. de Biología Vegetal
Universidad Politécnica de Madrid
Madrid, España


	[[alternative HTML version deleted]]

