[R] presence/absence similarities

[Galanidis Alexandros]

Greetings to all,

I have presence/absence data for species in plots in different years. My matrices looks like that:

YEAR1
    sp1  sp2  sp3  sp4 
1    1     1      0     1     
2    1     1      1     1      
3    1     1      0     1     
4    1     1      0     1     
5    1     1      0     1      

YEAR2
   sp1  sp2  sp3  sp4 
1    0     1      0     1     
2    1     1      1     1      
3    0     1      0     0     
4    1     0      1     1     
5    1     1      0     1      


I tried 'distance' in {ecodist}, 'vegdist' in {vegan}, 'jaccard' in {prabclus}, 'clujaccard' in {fpc} and others. The thing is that I don't understand the comparisons its method does, and consequently the outcome of the calculations. My final aim is to test for compositional disimilarity, doing a Mantel correlation Analysis, based on Jaccard similarities for matrices of species presences/absences between plots within a year and between years within plots.

thanks




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Dr. Alexandros Galanidis
Biodiversity Conservation Laboratory
Department of Environment
University of the Aegean
GR-811 00, Mytilene, Lesbos, Greece
Tel. +30 22510 36215
Fax. +30 22510 36296
Email: agal at env.aegean.gr