警告信息：在`...`：无效因子级别，NA生成

Question

警告信息：在`...`：无效因子级别，NA生成

我不明白为什么我收到这条警告信息。

> 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

Answer 1

警告消息是因为您的“类型”变量是一个因素而“午餐”不是定义的级别。stringsAsFactors = FALSE在创建数据框时使用标志强制“类型”为字符。>&nbsp;fixed&nbsp;<-&nbsp;data.frame("Type"&nbsp;=&nbsp;character(3),&nbsp;"Amount"&nbsp;=&nbsp;numeric(3))>&nbsp;str(fixed)'data.frame':&nbsp;&nbsp;&nbsp;3&nbsp;obs.&nbsp;of&nbsp;&nbsp;2&nbsp;variables: &nbsp;$&nbsp;Type&nbsp;&nbsp;:&nbsp;Factor&nbsp;w/&nbsp;1&nbsp;level&nbsp;"":&nbsp;NA&nbsp;1&nbsp;1 &nbsp;$&nbsp;Amount:&nbsp;chr&nbsp;&nbsp;"100"&nbsp;"0"&nbsp;"0">&nbsp;>&nbsp;fixed&nbsp;<-&nbsp;data.frame("Type"&nbsp;=&nbsp;character(3),&nbsp;"Amount"&nbsp;=&nbsp;numeric(3),stringsAsFactors=FALSE)>&nbsp;fixed[1,&nbsp;]&nbsp;<-&nbsp;c("lunch",&nbsp;100)>&nbsp;str(fixed)'data.frame':&nbsp;&nbsp;&nbsp;3&nbsp;obs.&nbsp;of&nbsp;&nbsp;2&nbsp;variables: &nbsp;$&nbsp;Type&nbsp;&nbsp;:&nbsp;chr&nbsp;&nbsp;"lunch"&nbsp;""&nbsp;"" &nbsp;$&nbsp;Amount:&nbsp;chr&nbsp;&nbsp;"100"&nbsp;"0"&nbsp;"0"

Answer 2

如果您直接从CSV文件中阅读，请执行此操作。myDataFrame&nbsp;<-&nbsp;read.csv("path/to/file.csv",&nbsp;header&nbsp;=&nbsp;TRUE,&nbsp;stringsAsFactors&nbsp;=&nbsp;FALSE)