为什么`cumsum'在ggplot中的组或构面中不起作用? [英] Why `cumsum` doesn't work within groups or facets in ggplot?

问题描述

来自在ggplot2中绘制累计计数的示例

x <- data.frame(A=replicate(200,sample(c("a","b","c"),1)),X=rnorm(200))
ggplot(x,aes(x=X,color=A)) + stat_bin(aes(y=cumsum(..count..)),geom="step")

如您所见，cumsum可跨组&方面.我想知道为什么会这样吗?显然，..count..是在组内完成的，为什么当将cumsum应用于..count..时却没有? ggplot是否在内部将所有..count..归入一个向量，然后对其应用cumsum?

As you can see, cumsum work across groups & facets. I am wondering why it does that? Clearly ..count.. is done within groups, why cumsum is not when applied on to ..count..? Does ggplot internally cat all ..count.. into a vector and then apply cumsum to it?

如何在不进行预处理的情况下正确解决该问题，例如使用plyr?

How to correctly resolve it without pre processing, e.g. using plyr?

我不介意geom不是step，只要图形是累积图，它就可以是line甚至是bar.

And I don't mind geom is not step, it can be line or even bar as long as the graph is a cumulative plot.

推荐答案

这是我用一行代码(ddply和mutate)处理此问题的方法:

Here's how I handle this with one line of code (ddply and mutate):

df <- data.frame(x=rnorm(1000),kind=sample(c("a","b","c"),1000,replace=T),
         label=sample(1:5,1000,replace=T),attribute=sample(1:2,1000,replace=T))

dfx <- ddply(df,.(kind,label,attribute),mutate,cum=rank(x)/length(x))

ggplot(dfx,aes(x=x))+geom_line(aes(y=cum,color=kind))+facet_grid(label~attribute)

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