R - geom_density() 使用什么算法以及如何提取曲线的点/方程? [英] R - What algorithm does geom_density() use and how to extract points/equation of curves?

问题描述

我想知道 geom_density() 到底在做什么，所以我证明了图形的合理性，以及是否有任何方法可以提取为所绘制的每条曲线生成的函数或点.

I would like to know what is geom_density() exactly doing, so I justify the graph and if there is any way of extracting the function or points that generates for each of the curves being plotted.

谢谢

推荐答案

Typing get("compute_group", ggplot2::StatDensity)(或者，以前，get("calculate",ggplot2:::StatDensity)) 将为您提供用于计算密度的算法.(从根本上说，它是对 density() 的调用，默认为 kernel="gaussian".)

Typing get("compute_group", ggplot2::StatDensity) (or, formerly, get("calculate", ggplot2:::StatDensity)) will get you the algorithm used to calculate the density. (At root, it's a call to density() with kernel="gaussian" the default.)

绘图中使用的点由 print.ggplot() 隐形返回，因此您可以像这样访问它们:

The points used in the plot are invisibly returned by print.ggplot(), so you can access them like this:

library(ggplot2)
m <- ggplot(movies, aes(x = rating))
m <- m + geom_density()
p <- print(m)
head(p$data[[1]], 3)
#           y      x   density   scaled  count PANEL group ymin      ymax
# 1 0.0073761 1.0000 0.0073761 0.025917 433.63     1     1    0 0.0073761
# 2 0.0076527 1.0176 0.0076527 0.026888 449.88     1     1    0 0.0076527
# 3 0.0078726 1.0352 0.0078726 0.027661 462.81     1     1    0 0.0078726


## Just to show that those are the points you are after, 
## extract and use them to create a lattice xyplot 
library(gridExtra)
library(lattice)
mm <- xyplot(y ~x, data=p$data[[1]], type="l")

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