Question

> test <- data.frame()
> test<-rbind(test,c("hi","i","am","bob"))
> test<-rbind(test,c("hi","i","am","alice"))
Warning message:
In `[<-.factor`(`*tmp*`, ri, value = "alice") :
  invalid factor level, NAs generated

为什么这个最小的例子会产生错误？我想将几个字符串行附加到空数据框。

Answer 1

您可以将信息存储在字符矩阵中。当然，您可以使用as.data.frame和参数stringsAsFactors = FALSE将此矩阵转换为数据框。

> test <- matrix(c("hi","i","am","bob"), nrow = 1)
> test <- rbind(test, c("hi","i","am","alice"))
> test
     [,1] [,2] [,3] [,4]   
[1,] "hi" "i"  "am" "bob"  
[2,] "hi" "i"  "am" "alice"

> testDF <- as.data.frame(test, stringsAsFactors = FALSE)
> testDF <- rbind(testDF, c("hi","i","am","happy"))
> testDF
  V1 V2 V3    V4
1 hi  i am   bob
2 hi  i am alice
3 hi  i am happy

Answer 2

问题在于，默认情况下，R将字符理解为因子。为了避免这种行为：

options(stringsAsFactors = FALSE)
test <- data.frame()
test<-rbind(test,c("hi","i","am","bob"))
test<-rbind(test,c("hi","i","am","alice"))

rbind char矢量到数据框

2 个答案: