R语言函数问题 ，求各位帮帮忙，作业，

[java大白666]

SplitInfo<-function(data,first,second){

result<-data.frame() #结果用数据框表示

for(i in 1:length(data[,1])){ #data中的每一行都做一次循环

if(data[i,first]==second){ #如果指定的data

result<-rbind(result,data[i,-first]) } #将划分属性相同的其他属性分类在一起，如age中youth相同的其他属性分类在一个数据框中

}

return(result)

}

> data
x y z
[1,] "1" "1" "1" "y"
[2,] "2" "1" "1" "y"
[3,] "3" "1" "0" "n"
[4,] "4" "0" "1" "n"
[5,] "5" "1" "1" "n"

报错：SplitInfo(data,2,1)
X.1. X.1..1 X.y.
1 1 1 y
2 <NA> 1 y
3 <NA> <NA> <NA>
4 <NA> 1 <NA>
Warning messages:
1: In `[<-.factor`(`*tmp*`, ri, value = "2") :
invalid factor level, NA generated
2: In `[<-.factor`(`*tmp*`, ri, value = "3") :
invalid factor level, NA generated
3: In `[<-.factor`(`*tmp*`, ri, value = "0") :
invalid factor level, NA generated
4: In `[<-.factor`(`*tmp*`, ri, value = "n") :
invalid factor level, NA generated
5: In `[<-.factor`(`*tmp*`, ri, value = "5") :
invalid factor level, NA generated
6: In `[<-.factor`(`*tmp*`, ri, value = "n") :
invalid factor level, NA generated

哪有问题，求帮忙告知啊

[java大白666]

为什么会显示成Na Na应该是其他数据，为什么不显示啊

[java大白666]

?????????????

[萝卜丝皮尔]

你赋值的值是原来属性中所没有的？