R 错误：一元运算符的参数无效

我看到了。 我有如下数据：

female=c("hw","hw","uw","uw","w","w")
male=c("w","hw","uw","w")

我需要为男性和女性制作一个柱状图，所以我制作了两个不同的数据框：

male<-data.frame(class=male)
female<-data.frame(class=female)

但它抱怨：

一元运算符的参数无效

---

我需要用绿色绘制男性绘图，用蓝色绘制女性绘图。

如果运行男性$class，它会给出空值，因此我不确定您在那里尝试做什么。也许是这样的：

df=data.frame(gender=as.factor(c(rep("female",6),rep("male",4))),
  outcome=as.character(c("hw","hw","uw","uw","w","w","w","hw","uw","w")))

library(ggplot2)

ggplot(data=df,aes(x=outcome,fill=gender)) + 
  geom_histogram(stat="count",position="dodge") + scale_fill_manual(values=c("blue","green"))

df=data.frame(gender=as.factor(c(rep("female",6),rep("male",4))),
  outcome=as.character(c("hw","hw","uw","uw","w","w","w","hw","uw","w")))

library(ggplot2)

ggplot(data=df,aes(x=outcome,fill=gender)) + 
  geom_histogram(stat="count",position="dodge") + scale_fill_manual(values=c("blue","green"))