参数化的ggplot2直方图/密度AES函数找不到对象

Ken Lin 发表于 Dev

Ken Lin

我创建了一个直方图/密度图函数，我希望对y轴进行计数而不是密度，但是在参数化其binwidth时遇到了问题。

我使用基于http://docs.ggplot2.org/current/geom_histogram.html的示例来说明我的尝试。

这是成功的plotMovies1函数。我按照引用的url来制作y轴..count ..而不是..density ..请注意，它在两个地方使用了硬编码的.5 binwidth，这就是我要参数化的...

# I want y axis as count, rather than density, and followed
# https://stat.ethz.ch/pipermail/r-help/2011-June/280588.html
plotMovies1 <- function() {
  m <- ggplot(movies, aes(x = rating))
  m <- m + geom_histogram(binwidth = .5)
  m <- m + geom_density(aes(y = .5 * ..count..))
}

直方图/密度（计数为y轴）和硬编码二进制宽度

我的第一次，未能在在本地BW参数化binwidth天真尝试plotMovies2 ...

# Failed first attempt to parameterize binwidth
plotMovies2 <- function() {
  bw <- .5
  m <- ggplot(movies, aes(x = rating))
  m <- m + geom_histogram(binwidth = bw)
# Error in eval(expr, envir, enclos) : object 'bw' not found 
  m <- m + geom_density(aes(y = bw * ..count..))
}
> print(plotMovies2())
Error in eval(expr, envir, enclos) : object 'bw' not found

我看讨论关于通过当地的环境，在ggplot AES在https://github.com/hadley/ggplot2/issues/743，但plotMovies3也无法以同样的方式，未能找到BW对象...

# Failed second attempt to parameterize binwidth, even after establishing
# aes environment, per https://github.com/hadley/ggplot2/issues/743
plotMovies3 <- function() {
  bw <- .5
  m <- ggplot(movies, aes(x = rating), environment = environment())
  m <- m + geom_histogram(binwidth = bw)
# Error in eval(expr, envir, enclos) : object 'bw' not found 
  m <- m + geom_density(aes(y = bw * ..count..))
}
> print(plotMovies3())
Error in eval(expr, envir, enclos) : object 'bw' not found

我终于尝试设置一个全球性的，但它仍然无法找到对象...

# Failed third attempt using global binwidth
global_bw <<- .5
plotMovies4 <- function() {
  m <- ggplot(movies, aes(x = rating), environment = environment())
  m <- m + geom_histogram(binwidth = global_bw)
# Error in eval(expr, envir, enclos) : object 'global_bw' not found 
  m <- m + geom_density(aes(y = global_bw * ..count..))
}
> print(plotMovies4())
Error in eval(expr, envir, enclos) : object 'global_bw' not found

给定plotMovies3和plotMovies4，我想这不是一个直接的环境问题。谁能阐明我该如何解决？同样，我的目标是能够创建直方图/密度图函数

它的y轴是计数而不是密度，并且
可以将其binwidth参数化（例如，用于操纵）

山

绝对不是很漂亮，但是如果您需要解决方法，可以使用常规density功能

plotMovies5 <- function(binw=0.5) {
  m <- ggplot(movies, aes(x = rating))
  m <- m + geom_histogram(binwidth = binw)
  wa <- density(x=movies$rating, bw = binw)
  wa <- as.data.frame(cbind(xvals = wa$x, yvals = wa$y * wa$n * binw))
  m <- m + geom_point(data = wa, aes(x = xvals, y = yvals))
}
print(plotMovies5(binw=0.25))

请注意，由于密度估计值并不完全相等，因此您仍需要对变量进行修补，如下所示：

binw = 0.5
m <- ggplot(movies, aes(x = rating))
m <- m + geom_density(aes(y = 0.5 * ..count..))
wa <- density(x=movies$rating, bw = binw)
wa <- as.data.frame(cbind(xvals = wa$x, yvals = wa$y * wa$n * binw))
m <- m + geom_point(data = wa, aes(x = xvals, y = yvals))
m

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