Finds the Mahalanobis Distance for a set of columns

TERR_Expression_Function_Mahalanobis_Distance.r

###################################################################
# Takes an arbitrarily long list of input columns and returns a 
# boolean indicating whether or not each row is an outlier.
###################################################################

# create vector of inputs
inputs <- grep("^input[0-9]+$",ls(), value = TRUE)

# capture columns as a matrix
x <- sapply(inputs, function(y) {eval(parse(text = y))})

# find complete cases
cc <- complete.cases(x)

# column of complete cases
xcc <- x[cc,]

# column of Mahalanobis Dists
dists <- rep(NA, nrow(x))
dists[cc] <- mahalanobis(xcc, colMeans(xcc), cov(xcc))

# capture the output
output <- dists