density /diversity of points

Hi Marcelino, 

Was out of the office for a while...
Thanks for the help. I think this could work...but can you tell me what this line does?

diversity <- apply(mol.tab,1,function(x) sum(x>0)) 

i cant figure out how diversity is calculated here?

Thanks again for the help, 

matevz

-----Original Message-----
From: Marcelino de la Cruz [mailto:marcelino.delacruz at upm.es] 
Sent: Thursday, May 12, 2011 2:03 PM
To: Matev? Pavli?
Cc: r-sig-geo at r-project.org
Subject: Re: [R-sig-Geo] density /diversity of points

Hi all,



I have a point data set (SHP) with coordinates and a attribute (i.e. type of point).

These points are scattered around a fairly big area. What i would like to do is to find a sub-area where density of points sombined with the diversity of type is the biggest.

Does anyone have any idea iff this is somehowe possible to do in R? 
Any idea would be greatly aprpeciated,

   

To your first question:

library(fortunes)
fortune("Yoda")

;-)

More seriously, you could  transform your shp data in a ppp object with spatstat. See the vignette in spatstat. Then you can use some functions there, for example (with the data set lansing):

library(spatstat)
data(lansing)
plot(lansing)
# get an estimate of point density
lansing.den <- density.ppp(lansing)
plot(lansing.den)

# get an estimate of point diversity (here, for the shake of brevity, at the points themselves)
lansing.tab<- marktable(lansing,R=0.05)
diversity <- apply(lansing.tab,1,function(x) sum(x>0)) lansing.div <- setmarks(lansing,diversity) lansing.div.s <-smooth.ppp(lansing.div)

plot(lansing.div.s)

# select areas with arbitrary high values of  density and diversity plot(eval.im(lansing.div.s >4.5 & (lansing.den/max(lansing.den))>0.9))


HTH. Cheers,

Marcelino



--
_________________________________

Marcelino de la Cruz Rot
Departamento de Biologia Vegetal
E.U.T.I. Agricola
Universidad Politecnica de Madrid
  28040 Madrid
  Tel: 34913365654
  _________________________________