无效的因子水平，生成NA警告。

Question

无效的因子水平，生成NA警告。

4

与这里提出的另一个问题类似，我收到了主题行中的错误消息。我试图使用它的解决方法来解决我的问题，但我无法做到这一点。这是我的代码：

#Change the format of IED deaths to be uniform
USdata$Cause[USdata$Cause=="Hostile - hostile fire - IED attack" | USdata$Cause=="Hostile - hostile fire - IED attack (suicide attack)" | USdata$Cause=="Hostile - hostile fire - IED attack (suicide car bomb)" | USdata$Cause=="Hostile - hostile fire - IED attack (while defusing)" | USdata$Cause=="Hostile - hostile fire - IED attack, RPG" | USdata$Cause=="Hostile - hostile fire - IED attack, RPG, small arms fire" | USdata$Cause=="Hostile - hostile fire - IED Attack, small arms fire" | USdata$Cause=="Hostile - hostile fire - IED Attack, small arms fire, indirect fire"] <- "Hostile - IED Attack"

Warning message:
In `[<-.factor`(`*tmp*`, USdata$Cause == "Hostile - hostile fire - IED attack" |  :
 invalid factor level, NA generated

当我总结我的尝试新值“Hostile-IED Attack”时，我发现所有的返回值都是NA。我能做类似的事情来处理其他值，但这一个不那么容易。谢谢。

- Sean Sharp

4

当使用read.table或read.csv读取数据时，需使用stringsAsFactors=FALSE，以避免将字符向量转换为因子（factor）。 - akrun

1个回答

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- hrbrmstr · Accepted Answer

首先将其转换为因子，进行更改后再重新转换回来。此外，在长期运行中 %in% 可能会更有效：

ied_causes <- c("Hostile - hostile fire - IED attack",
                "Hostile - hostile fire - IED attack (suicide attack)",
                "Hostile - hostile fire - IED attack (suicide car bomb)",
                "Hostile - hostile fire - IED attack (while defusing)",
                "Hostile - hostile fire - IED attack, RPG",
                "Hostile - hostile fire - IED attack, RPG, small arms fire",
                "Hostile - hostile fire - IED Attack, small arms fire",
                "Hostile - hostile fire - IED Attack, small arms fire, indirect fire")

USdata$Cause <- as.character(USdata$Cause)
USdata$Cause[USdata$Cause %in% ied_causes] <- "Hostile - IED Attack"
USdata$Cause <- factor(USdata$Cause)