警告消息:在 `...` 中:因子水平无效，NA 生成 [英] Warning message: In `...` : invalid factor level, NA generated

问题描述

我不明白为什么会收到这条警告消息.

I don't understand why I got this warning message.

> fixed <- data.frame("Type" = character(3), "Amount" = numeric(3))
> fixed[1, ] <- c("lunch", 100)
Warning message:
In `[<-.factor`(`*tmp*`, iseq, value = "lunch") :
  invalid factor level, NA generated
> fixed
  Type Amount
1 <NA>    100
2           0
3           0

推荐答案

出现警告消息是因为您的类型"变量已成为一个因素，而午餐"不是一个定义的级别.使数据框强制类型"为字符时，请使用 stringsAsFactors = FALSE 标志.

The warning message is because your "Type" variable was made a factor and "lunch" was not a defined level. Use the stringsAsFactors = FALSE flag when making your data frame to force "Type" to be a character.

> fixed <- data.frame("Type" = character(3), "Amount" = numeric(3))
> str(fixed)
'data.frame':   3 obs. of  2 variables:
 $ Type  : Factor w/ 1 level "": NA 1 1
 $ Amount: chr  "100" "0" "0"
> 
> fixed <- data.frame("Type" = character(3), "Amount" = numeric(3),stringsAsFactors=FALSE)
> fixed[1, ] <- c("lunch", 100)
> str(fixed)
'data.frame':   3 obs. of  2 variables:
 $ Type  : chr  "lunch" "" ""
 $ Amount: chr  "100" "0" "0"

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