[R] SDMTools package - calculating overlap?

[David Winsemius]

On Jul 18, 2011, at 9:40 AM, Ana Kolar wrote:

> Dear R users,
>
> Any idea of how to calculate an area of an overlap between two  
> functions? The only R build in function that I found is I Similarity  
> Statistic for Quantifying Niche Overlap and I am really not sure if  
> this function is producing exactly what I am interested in since I  
> was plotting functions and often got confused results (for example:  
> got high value for the overlap of one pair and low for the other  
> pair, while from the plot it looked like the first pair was  
> overlapping better.) Can anyone please explain what's the reason  
> behind such a behaviour? And does anyone has a suggestion of what  
> function could be used for a calculation of an overlap area? The  
> problem with 'Istat' function is also that it requires both data  
> sets to have the same length, while I would be more interested in a  
> function that enables overlap calculation even if data sets have  
> different length. Looking forward to hearing from you! Have a good  
> day. Ana

Shouldn't you be integrating their difference (or the absolute value  
of their differences depending on your definition of "overlap"). I  
fail in understanding your example. Where is/are the function(s)?

>
> library(SDMTools)
> a <- matrix(runif(30))
> b <- matrix(runif(30))
> Istat(a,b)
> 	[[alternative HTML version deleted]]
-- 

David Winsemius, MD
West Hartford, CT