Dispersion (H-prime)
Calculates the dispersion ("rarity") of targets associated with planning units
dispersion(x)
x |
data.frame object of target values |
data.frame with columns H values for each target, H , sH, sHmax
The dispersion index (H-prime) is calculated H = sum( sqrt(p) / sqrt(a) ) where; P = [sum of target in planning unit / sum of target across all planning units] and a = [count of planning units containing target / number of planning units]
Jeffrey S. Evans <jeffrey_evans@tnc.org>
Evans, J.S., S.R. Schill, G.T. Raber (2015) A Systematic Framework for Spatial Conservation Planning and Ecological Priority Design in St. Lucia, Eastern Caribbean. Chapter 26 in Central American Biodiversity : Conservation, Ecology and a Sustainable Future. F. Huettman (eds). Springer, NY.
library(sp)
data(pu)
d <- dispersion(pu@data[,2:ncol(pu)])
p <- d[,"H"]
clr <- c("#3288BD", "#99D594", "#E6F598", "#FEE08B",
"#FC8D59", "#D53E4F")
clrs <- ifelse(p < 0.5524462, clr[1],
ifelse(p >= 0.5524462 & p < 1.223523, clr[2],
ifelse(p >= 1.223523 & p < 2.465613, clr[3],
ifelse(p >= 2.465613 & p < 4.76429, clr[4],
ifelse(p >= 4.76429 & p < 8.817699, clr[5],
ifelse(p >= 8.817699, clr[6], NA))))))
plot(pu, col=clrs, border=NA)
legend("topleft", legend=rev(c("Very Rare","Rare","Moderately Rare",
"Somewhat Common","Common","Over Dispersed")),
fill=clr, cex=0.6, bty="n")
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