KNN one factor predicting problem

Could anybody help me out please?

cl<-as.factor(traindata[,13])
knn(traindata[1:295,2], newdata[1:32,2], cl,k=2,

prob=TRUE) 
Error in knn(traindata[1:295, 2], newdata[1:32, 2],
cl, k = m, prob = TRUE) : 
        Dims of test and train differ

Both traindata and newdata have 13 elements. Only one
of the first 12 elemnets is needed to predict the 13
element.
What's the problem of following commands?

Thank you very much indeed

Qin