Warning messages:
1: In eval(expr, envir, enclos) : NAs introduced by coercion
2: In eval(expr, envir, enclos) : NAs introduced by coercion
3: In eval(expr, envir, enclos) : NAs introduced by coercion
4: In eval(expr, envir, enclos) : NAs introduced by coercion
5: In eval(expr, envir, enclos) : NAs introduced by coercion
6: In eval(expr, envir, enclos) : NAs introduced by coercion
7: In eval(expr, envir, enclos) : NAs introduced by coercion
8: In eval(expr, envir, enclos) : NAs introduced by coercion
9: In eval(expr, envir, enclos) : NAs introduced by coercion