【发布时间】：2018-12-26 11:09:30
【问题描述】：
我正处于学习如何扩展ggplot2 的早期阶段。我想创建一个自定义geom 和关联的stat。我的出发点是vignette。此外，我还受益于this 和this。我正在尝试制作一个模板来教自己，并希望能教给其他人。
主要问题：
在我的函数calculate_shadows() 中，所需的参数params$anchor 是NULL。如何访问它？
下面描述的目标仅用于学习如何创建自定义 stat 和 geom 函数，这不是一个真正的目标：从屏幕截图中可以看出，我确实知道如何利用 @987654336 的力量@ 制作图表。
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geom将读取数据，并且对于提供的变量("x", "y")将绘制（因为需要更好的词）shadows：水平线min(x)--max(x)在默认y=0和垂直线 @ 987654342@ 默认为x=0。如果提供了选项，则可以更改这些“锚点”，例如如果用户提供x = 35, y = 1，则将在截距y = 1处绘制水平线，而在截距x = 35处绘制垂直线。用法：library(ggplot2) ggplot(data = mtcars, aes(x = mpg, y = wt)) + geom_point() + geom_shadows(x = 35, y = 1)
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stat将读取数据，对于提供的变量，("x", "y")将根据stat的值计算shadows。例如，通过传递stat = "identity"，将为数据的最小值和最大值计算阴影（由geom_shadows完成）。但是通过stat = "quartile"，将计算第一和第三四分位数的阴影。更一般地说，可以传递一个像stats::quantile这样的函数，参数为args = list(probs = c(0.10, 0.90), type = 6)，以使用第 10 和第 90 个百分位数以及类型 6 的分位数方法来计算阴影。用法：ggplot(data = mtcars, aes(x = mpg, y = wt)) + geom_point() + stat_shadows(stat = "quartile")
不幸的是，我对扩展 ggplot2 不熟悉，这使我无法实现目标。这些图是用geom_segment“伪造”的。基于上面引用的教程和讨论并检查现有代码（如stat-qq 或stat-smooth），我已经为这个目标构建了一个基本架构。一定有很多错误，不胜感激。另外，请注意，这些方法中的任何一种都可以：geom_shadows(anchor = c(35, 1)) 或 geom_shadows(x = 35, y = 1)。
现在这是我的努力。首先，geom-shadows.r 定义geom_shadows()。二、stat-shadows.r定义stat_shadows()。代码不能按原样工作。但如果我执行它的内容，它确实会产生所需的统计数据。为了清楚起见，我已经删除了stat_shadows() 中的大部分计算，例如四分位数，以专注于要领。布局有什么明显的错误吗？
geom-shadows.r
#' documentation ought to be here
geom_shadows <- function(
mapping = NULL,
data = NULL,
stat = "shadows",
position = "identity",
...,
anchor = list(x = 0, y = 0),
shadows = list("x", "y"),
type = NULL,
na.rm = FALSE,
show.legend = NA,
inherit.aes = TRUE) {
layer(
data = data,
mapping = mapping,
stat = stat,
geom = GeomShadows,
position = position,
show.legend = show.legend,
inherit.aes = inherit.aes,
params = list(
anchor = anchor,
shadows = shadows,
type = type,
na.rm = na.rm,
...
)
)
}
GeomShadows <- ggproto("GeomShadows", Geom,
# set up the data, e.g. remove missing data
setup_data = function(data, params) {
data
},
# set up the parameters, e.g. supply warnings for incorrect input
setup_params = function(data, params) {
params
},
draw_group = function(data, panel_params, coord, anchor, shadows, type) {
# draw_group uses stats returned by compute_group
# set common aesthetics
geom_aes <- list(
alpha = data$alpha,
colour = data$color,
size = data$size,
linetype = data$linetype,
fill = alpha(data$fill, data$alpha),
group = data$group
)
# merge aesthetics with data calculated in setup_data
geom_stats <- new_data_frame(c(list(
x = c(data$x.xmin, data$y.xmin),
xend = c(data$x.xmax, data$y.xmax),
y = c(data$x.ymin, data$y.ymin),
yend = c(data$x.ymax, data$y.ymax),
alpha = c(data$alpha, data$alpha)
), geom_aes
), n = 2)
# turn the stats data into a GeomPath
geom_grob <- GeomSegment$draw_panel(unique(geom_stats),
panel_params, coord)
# pass the GeomPath to grobTree
ggname("geom_shadows", grobTree(geom_grob))
},
# set legend box styles
draw_key = draw_key_path,
# set default aesthetics
default_aes = aes(
colour = "blue",
fill = "red",
size = 1,
linetype = 1,
alpha = 1
)
)
stat-shadows.r
#' documentation ought to be here
stat_shadows <-
function(mapping = NULL,
data = NULL,
geom = "shadows",
position = "identity",
...,
# do I need to add the geom_shadows arguments here?
anchor = list(x = 0, y = 0),
shadows = list("x", "y"),
type = NULL,
na.rm = FALSE,
show.legend = NA,
inherit.aes = TRUE) {
layer(
stat = StatShadows,
data = data,
mapping = mapping,
geom = geom,
position = position,
show.legend = show.legend,
inherit.aes = inherit.aes,
params = list(
# geom_shadows argument repeated here?
anchor = anchor,
shadows = shadows,
type = type,
na.rm = na.rm,
...
)
)
}
StatShadows <-
ggproto("StatShadows", Stat,
# do I need to repeat required_aes?
required_aes = c("x", "y"),
# set up the data, e.g. remove missing data
setup_data = function(data, params) {
data
},
# set up parameters, e.g. unpack from list
setup_params = function(data, params) {
params
},
# calculate shadows: returns data_frame with colnames: xmin, xmax, ymin, ymax
compute_group = function(data, scales, anchor = list(x = 0, y = 0), shadows = list("x", "y"), type = NULL, na.rm = TRUE) {
.compute_shadows(data = data, anchor = anchor, shadows = shadows, type = type)
}
)
# Calculate the shadows for each type / shadows / anchor
.compute_shadows <- function(data, anchor, shadows, type) {
# Deleted all type-checking, etc. for MWE
# Only 'type = c(double, double)' accepted, e.g. type = c(0, 1)
qs <- type
# compute shadows along the x-axis
if (any(shadows == "x")) {
shadows.x <- c(
xmin = as.numeric(stats::quantile(data[, "x"], qs[[1]])),
xmax = as.numeric(stats::quantile(data[, "x"], qs[[2]])),
ymin = anchor[["y"]],
ymax = anchor[["y"]])
}
# compute shadows along the y-axis
if (any(shadows == "y")) {
shadows.y <- c(
xmin = anchor[["x"]],
xmax = anchor[["x"]],
ymin = as.numeric(stats::quantile(data[, "y"], qs[[1]])),
ymax = as.numeric(stats::quantile(data[, "y"], qs[[2]])))
}
# store shadows in one data_frame
stats <- new_data_frame(c(x = shadows.x, y = shadows.y))
# return the statistics
stats
}
.
【问题讨论】：
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这个问题被编辑以反映最重要的问题：特别是，我修复了
draw_group在合并美学与数据时的明显问题。代码主要基于geom_boxplot和stat_boxplot，尤其是whiskers。 -
请注意，要编译上面的代码，您需要在特殊函数前面加上
ggplot2::并复制new_data_frame之类的函数，或者（这就是我所做的）克隆ggplot2包并在NAMESPACE和DESCRIPTION中添加并正确引用上述两个文件进行编译