scripts/algorithms/naive-bayes-predict.dml

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# Implements scoring with a naive Bayes model learnt using
# naive-bayes.dml
#
# hadoop jar SystemML.jar -f naive-bayes-predict.dml -nvargs X=data Y=labels prior=model_file1 conditionals=model_file2 probabilities=probabilities accuracy=accuracy confusion=confusion fmt="text"
#

cmdLine_Y = ifdef($Y, " ")
cmdLine_accuracy = ifdef($accuracy, " ")
cmdLine_confusion = ifdef($confusion, " ")
cmdLine_fmt = ifdef($fmt, "text")

D = read($X)
min_feature_val = min(D)
if(min_feature_val < 0)
	stop("Stopping due to invalid argument: Multinomial naive Bayes is meant for count-based feature values, minimum value in X is negative")

prior = read($prior)

dimensions = as.scalar(prior[nrow(prior),1])
prior = prior[1:(nrow(prior)-1),]

conditionals = read($conditionals)

numRows = nrow(D)

ones = matrix(1, rows=numRows, cols=1)
D_w_ones = append(D, ones)
model = append(conditionals, prior)

log_probs = D_w_ones %*% t(log(model))


mx = rowMaxs(log_probs)
ones = matrix(1, rows=1, cols=nrow(prior))
probs = log_probs - mx %*% ones
probs = exp(probs)/(rowSums(exp(probs)) %*% ones)
write(probs, $probabilities, format=cmdLine_fmt)


if(cmdLine_Y != " "){
	C = read(cmdLine_Y)
	if(min(C) < 1)
		stop("Stopping due to invalid argument: Label vector (Y) must be recoded")
	
	pred = rowIndexMax(log_probs)
	acc = sum(pred == C) / numRows * 100

	acc_str = "Accuracy (%): " + acc
	print(acc_str)
	if(cmdLine_accuracy != " ")
		write(acc, cmdLine_accuracy)

	num_classes = nrow(prior)
	num_classes_ground_truth = max(C)
	if(num_classes < num_classes_ground_truth)
		num_classes = num_classes_ground_truth
		
	if(cmdLine_confusion != " "){
		confusion_mat = table(pred, C, num_classes, num_classes)
		write(confusion_mat, cmdLine_confusion, format="csv")
	}
}