# row x column combinations existing
DT <- data.frame(Row=sort(rep(1:10,5)), Col=rep(1:5,10))
DT$Rowf <- as.factor(DT$Row)
DT$Colf <- as.factor(DT$Col)
DT <- DT[-1,] # remove one intentionally
simage(data=DT, Var1 = "Rowf", Var2 = "Colf")
# you can also inpect which cross combinations exist
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