(Dis)similarity of two populations
Measures of niche overlap are used to assess the similarity or dissimilarity of two populations. The overlap coefficient is a similarity measure related to the Jaccard index that computes the overlap between two sets. Here, we consider two different implementations of the overlap coefficient: Matusita's measure and Morisita's measure.
An example is given below.
a=rnorm(1000,5,10)
b=rnorm(45,9,8)
ovl = overlap(a,b)
plot(density(a),main="Niche Overlap",xlim=c(-30,40),ylim=c(0,0.05))
lines(density(b),col="green")
polygon(density(a)$x, density(a)$y, col = rgb(0,1,0, .5))
polygon(density(b)$x, density(b)$y, col = rgb(0.50,0,0.50, .5))
text(-30,0.05,paste("Proportional similarity measure:",round(ovl$prop*100,2),"%"),col="black",pos=4)
text(-30,0.048,paste("Matusita's Measure:",round(ovl$rho,2)),col="black",pos=4)
text(-30,0.046,paste("Morisita's Measure:",round(ovl$lambda,2)),col="black",pos=4)
text(-30,0.044,paste("Hellinger Distance:",round(ovl$hellinger,2)),col="black",pos=4)
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