R package caret confusionMatrix with missing categories

Question

I am using the function confusionMatrix in the R package caret to calculate some statistics for some data I have. I have been put

Answer 1

You can use union to ensure similar levels:

library(caret)

# Sample Data
predicted <- c(1,2,1,2,1,2,1,2,3,4,3,4,6,5) # Levels 1,2,3,4,5,6
reference <- c(1,2,1,2,1,2,1,2,1,2,1,3,3,4) # Levels 1,2,3,4

u <- union(predicted, reference)
t <- table(factor(predicted, u), factor(reference, u))
confusionMatrix(t)