Adjusted Rand Index

Computes the adjusted Rand index comparing two classifications.

Usage

adjustedRandIndex(x, y)

Arguments

x

A numeric or character vector of class labels.

y

A numeric or character vector of class labels. The length of y should be the same as that of x.

Value

The adjusted Rand index comparing the two partitions (a scalar). This index has zero expected value in the case of random partition, and it is bounded above by 1 in the case of perfect agreement between two partitions.

References

L. Hubert and P. Arabie (1985) Comparing Partitions, Journal of the Classification, 2, pp. 193-218.

See also

classError, mapClass, table

Examples

a <- rep(1:3, 3)
a
#> [1] 1 2 3 1 2 3 1 2 3
b <- rep(c("A", "B", "C"), 3)
b
#> [1] "A" "B" "C" "A" "B" "C" "A" "B" "C"
adjustedRandIndex(a, b)
#> [1] 1

a <- sample(1:3, 9, replace = TRUE)
a
#> [1] 3 2 3 3 2 3 1 2 2
b <- sample(c("A", "B", "C"), 9, replace = TRUE)
b
#> [1] "A" "A" "B" "A" "B" "C" "C" "B" "B"
adjustedRandIndex(a, b)
#> [1] 0.08695652

a <- rep(1:3, 4)
a
#>  [1] 1 2 3 1 2 3 1 2 3 1 2 3
b <- rep(c("A", "B", "C", "D"), 3)
b
#>  [1] "A" "B" "C" "D" "A" "B" "C" "D" "A" "B" "C" "D"
adjustedRandIndex(a, b)
#> [1] -0.2790698

irisHCvvv <- hc(modelName = "VVV", data = iris[,-5])
cl3 <- hclass(irisHCvvv, 3)
adjustedRandIndex(cl3,iris[,5])
#> [1] 0.7591987

irisBIC <- mclustBIC(iris[,-5])
adjustedRandIndex(summary(irisBIC,iris[,-5])$classification,iris[,5])
#> [1] 0.5681159
adjustedRandIndex(summary(irisBIC,iris[,-5],G=3)$classification,iris[,5])
#> [1] 0.9038742