R 条形图不会显示，但会显示x轴和y轴以及标题

这是我的

barplot(table(ordered(cancer$agecat,
c("Younger than 31","31 to 41","42 to 54","55 or Older"))),
main="Ordered Bar Chart of Age Categorie",ylim=c(0,120),
xlab="Number of People In Each Category")

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这以前奏效了，一切都很好，但现在什么都没有了

看看cancer$agecat中的值，这可能就是原因。这是一个工作示例：

 barplot(runif(4), names.arg = ordered(c("Younger than 31","31 to 41","42 to 54","55 or Older")),
         main="Ordered Bar Chart of Age Categorie",ylim=c(0,1),
         xlab="Number of People In Each Category") 

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请提供一个最小的可复制示例。看到和