Create bhattacharyya-distance.R

misc/sandbox/bhattacharyya-distance.R

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+
+
+# philentropy package
+# https://search.r-project.org/CRAN/refmans/philentropy/html/00Index.html
+
+# https://en.wikipedia.org/wiki/Bhattacharyya_distance
+
+library(philentropy)
+
+s <- seq(-3, 6, length.out = 100)
+x <- dnorm(s, mean = 0, sd = 1)
+y <- dnorm(s, mean = 1, sd = 1)
+z <- dnorm(s, mean = -0.1, sd = 1)
+
+plot(s, x, type = 'l', xlim = c(-3, 6))
+lines(s, y, col = 2)
+lines(s, z, col = 3)
+
+# absolute value depends on number of elements in x, y
+bhattacharyya(P = x, Q = y, testNA = FALSE, unit = "log2", epsilon = 0.00001)
+bhattacharyya(P = x, Q = z, testNA = FALSE, unit = "log2", epsilon = 0.00001)
+
+
+# can we use this to describe meaningful differences between GHL probability density curves?
+# what about depth functions?
+# what about spectra?
+
+# TODO: try it out on a couple soil-related things?
+library(aqp)
+
+
+data("munsell.spectra.wide")
+
+
+x <- munsell.spectra.wide[, '10YR 3/3']
+y <- munsell.spectra.wide[, '5YR 4/6']
+
+# useful?
+bhattacharyya(P = x, Q = y, testNA = FALSE, unit = "log2", epsilon = 0.00001)
+
+