knn中的错误：外部函数调用中的NA / NaN / Inf（arg 6）

Question

当我使用knn：

时，此错误的含义是什么？

g=summary(knn(train, test, l, k = 3))
Error in knn(train, test, l, k = 3) :
  NA/NaN/Inf in foreign function call (arg 6)

In addition: Warning messages:
1: In knn(train, test, l, k = 3) : NAs introduced by coercion
2: In knn(train, test, l, k = 3) : NAs introduced by coercion