src/test/scripts/functions/builtin/NaiveBayesPredict.R

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args <- commandArgs(TRUE)

library("Matrix")
library("naivebayes")

D = as.matrix(readMM(paste(args[1], "D.mtx", sep="")))
C = as.matrix(readMM(paste(args[1], "C.mtx", sep="")))
laplace <- as.numeric(args[3])

# divide D into "train" and "test" data
numRows = nrow(D)
trainSize = numRows * 0.8

trainData = D[1:trainSize, ]
testData = D[(trainSize+1):numRows, ]
y <- factor(C[1:trainSize])

# The Naive Bayes Predict need to unique column name
features <- paste0("V", seq_len(ncol(trainData)))
colnames(trainData) <- features
colnames(testData) <- features

# Create model base on train data
model <- multinomial_naive_bayes(x = trainData, y = y, laplace = laplace)

# The SystemDS DML scripts based on YRaw data
# and the "naivebayes" predict function in R
# return probabilities matrix
# Example: YRaw <- predict(model, newdata = testData, type = "prob")

# We need to return "Raw" values
lev <- model$levels
prior <- model$prior
params <- t(model$params)
YRaw <- tcrossprod(testData, log(params))

for (ith_class in seq_along(lev)) {
  YRaw[ ,ith_class] <- YRaw[ ,ith_class] + log(prior[ith_class])
}

Y <- max.col(YRaw, ties.method="last")

# write out the predict
writeMM(as(YRaw, "CsparseMatrix"), paste(args[4], "YRaw", sep=""))
writeMM(as(Y, "CsparseMatrix"), paste(args[4], "Y", sep=""))