将额外参数传递给 ggplot2 中的自定义 geom
Passing an extra parameter to a custom geom in ggplot2
我正在创建一个自定义 geom 并希望它采用一个额外的参数,称为 showpoints
,它对实际绘图有一些或其他的作用。例如,通过将其设置为 FALSE,geom 实际上是 returns a zeroGrob()
。我找到了一种方法,但是 (i) 它很笨重而且有点奇怪 (ii) 我不完全理解我在做什么,这是一个不好的迹象。问题是当你定义一个新的统计数据时,可以 运行 setup_params
,但是 geoms 没有它:
Compared to Stat and Position, Geom is a little different because the
execution of the setup and compute functions is split up. setup_data
runs before position adjustments, and draw_layer is not run until
render time, much later. This means there is no setup_params because
it's hard to communicate the changes.
基本上,我的代码的工作原理是您可以使用附加参数来抑制点的绘制:
# draw the points by default
ggplot(mpg, aes(displ, hwy)) + geom_simple_point()
# suppresses drawing of the points
ggplot(mpg, aes(displ, hwy)) + geom_simple_point(showpoints=FALSE)
到目前为止,这是我的代码,基于 extending ggplot2 tutorial:
## Return the grob to draw. The additional parameter,
## showpoints, determines whether a points grob should be returned,
## or whether zeroGrob() should take care of not showing the points
.draw_panel_func <- function(data, panel_params, coord) {
coords <- coord$transform(data, panel_params)
showpoints <- unique(data$showpoints)
cat("showpoints=", as.character(showpoints), "\n")
if(!is.null(showpoints) && is.logical(showpoints) && !showpoints) {
return(zeroGrob())
} else {
return(
grid::pointsGrob(coords$x, coords$y,
pch = coords$shape,
gp = grid::gpar(col = coords$colour))
)
}
}
## definition of the new geom. setup_data inserts the parameter
## into data, therefore making it accessible for .draw_panel_func
GeomSimplePoint <- ggproto("GeomSimplePoint", Geom,
required_aes = c("x", "y"),
default_aes = aes(shape = 19, colour = "black"),
draw_key = draw_key_point,
setup_data = function(data, params) {
if(!is.null(params$showpoints)) {
data$showpoints <- params$showpoints
}
data
},
extra_params = c("na.rm", "showpoints"),
draw_panel = .draw_panel_func
)
geom_simple_point <- function(mapping = NULL, data = NULL, stat = "identity",
position = "identity", na.rm = FALSE, show.legend = NA,
inherit.aes = TRUE, showpoints=TRUE, ...) {
layer(
geom = GeomSimplePoint, mapping = mapping, data = data, stat = stat,
position = position, show.legend = show.legend, inherit.aes = inherit.aes,
params = list(na.rm = na.rm, showpoints=showpoints, ...)
)
}
是否有更简单的方法将选定的额外参数传递给 geom?如果我可以定义 extra_params
,为什么我不能更轻松地访问它们?
有一个比较简单的方法,就是将额外的参数作为参数传递给面板绘制函数。这是一个适用于您的 geom_simple_point()
:
的简单示例
GeomSimplePoint <- ggproto(
"GeomSimplePoint",
GeomPoint,
extra_params = c("na.rm", "showpoints"),
draw_panel = function(data, panel_params,
coord, na.rm = FALSE, showpoints = TRUE) {
if (showpoints) {
return(GeomPoint$draw_panel(data, panel_params, coord, na.rm = na.rm))
} else {
return(zeroGrob())
}
}
)
顺便说一句,如果你想复制一个已经存在的 geom 的行为,比如 geom_point()
,设置你自己的 ggproto 对象来继承那个 geom 的 ggproto 对象会更容易。这样,您在 ggproto 中指定的默认 aes、必需的 aes 和其他参数会自动 copied/inherited 来自该 geom,您不必手动指定所有这些参数。
我正在创建一个自定义 geom 并希望它采用一个额外的参数,称为 showpoints
,它对实际绘图有一些或其他的作用。例如,通过将其设置为 FALSE,geom 实际上是 returns a zeroGrob()
。我找到了一种方法,但是 (i) 它很笨重而且有点奇怪 (ii) 我不完全理解我在做什么,这是一个不好的迹象。问题是当你定义一个新的统计数据时,可以 运行 setup_params
,但是 geoms 没有它:
Compared to Stat and Position, Geom is a little different because the execution of the setup and compute functions is split up. setup_data runs before position adjustments, and draw_layer is not run until render time, much later. This means there is no setup_params because it's hard to communicate the changes.
基本上,我的代码的工作原理是您可以使用附加参数来抑制点的绘制:
# draw the points by default
ggplot(mpg, aes(displ, hwy)) + geom_simple_point()
# suppresses drawing of the points
ggplot(mpg, aes(displ, hwy)) + geom_simple_point(showpoints=FALSE)
到目前为止,这是我的代码,基于 extending ggplot2 tutorial:
## Return the grob to draw. The additional parameter,
## showpoints, determines whether a points grob should be returned,
## or whether zeroGrob() should take care of not showing the points
.draw_panel_func <- function(data, panel_params, coord) {
coords <- coord$transform(data, panel_params)
showpoints <- unique(data$showpoints)
cat("showpoints=", as.character(showpoints), "\n")
if(!is.null(showpoints) && is.logical(showpoints) && !showpoints) {
return(zeroGrob())
} else {
return(
grid::pointsGrob(coords$x, coords$y,
pch = coords$shape,
gp = grid::gpar(col = coords$colour))
)
}
}
## definition of the new geom. setup_data inserts the parameter
## into data, therefore making it accessible for .draw_panel_func
GeomSimplePoint <- ggproto("GeomSimplePoint", Geom,
required_aes = c("x", "y"),
default_aes = aes(shape = 19, colour = "black"),
draw_key = draw_key_point,
setup_data = function(data, params) {
if(!is.null(params$showpoints)) {
data$showpoints <- params$showpoints
}
data
},
extra_params = c("na.rm", "showpoints"),
draw_panel = .draw_panel_func
)
geom_simple_point <- function(mapping = NULL, data = NULL, stat = "identity",
position = "identity", na.rm = FALSE, show.legend = NA,
inherit.aes = TRUE, showpoints=TRUE, ...) {
layer(
geom = GeomSimplePoint, mapping = mapping, data = data, stat = stat,
position = position, show.legend = show.legend, inherit.aes = inherit.aes,
params = list(na.rm = na.rm, showpoints=showpoints, ...)
)
}
是否有更简单的方法将选定的额外参数传递给 geom?如果我可以定义 extra_params
,为什么我不能更轻松地访问它们?
有一个比较简单的方法,就是将额外的参数作为参数传递给面板绘制函数。这是一个适用于您的 geom_simple_point()
:
GeomSimplePoint <- ggproto(
"GeomSimplePoint",
GeomPoint,
extra_params = c("na.rm", "showpoints"),
draw_panel = function(data, panel_params,
coord, na.rm = FALSE, showpoints = TRUE) {
if (showpoints) {
return(GeomPoint$draw_panel(data, panel_params, coord, na.rm = na.rm))
} else {
return(zeroGrob())
}
}
)
顺便说一句,如果你想复制一个已经存在的 geom 的行为,比如 geom_point()
,设置你自己的 ggproto 对象来继承那个 geom 的 ggproto 对象会更容易。这样,您在 ggproto 中指定的默认 aes、必需的 aes 和其他参数会自动 copied/inherited 来自该 geom,您不必手动指定所有这些参数。