11

我一直在阅读有关扩展 ggplot2的小插图，但我对如何制作可以向绘图添加多个几何图形的单个几何图形感到有点困惑。ggplot2 几何图形中已经存在多个几何图形，例如，我们有geom_contour（多条路径）和geom_boxplot（多条路径和点）之类的东西。但我不太明白如何将它们扩展到新的几何图形中。

假设我正在尝试geom_manythings通过在单个数据集上进行计算来绘制两个多边形和一个点。一个多边形将是所有点的凸包，第二个多边形将是点子集的凸包，单个点将代表数据的中心。我希望所有这些都与一个 geom 的调用一起出现，而不是三个单独的调用，正如我们在这里看到的：

# example data set
set.seed(9)
n <- 1000
x <- data.frame(x = rnorm(n),
                y = rnorm(n))

# computations for the geometries 
# chull for all the points
hull <-  x[chull(x),]
# chull for all a subset of the points
subset_of_x <- x[x$x > 0 & x$y > 0 , ]
hull_of_subset <- subset_of_x[chull(subset_of_x), ]
# a point in the centre of the data
centre_point <- data.frame(x = mean(x$x), y = mean(x$y))

# plot
library(ggplot2)
ggplot(x, aes(x, y)) +
  geom_point() + 
  geom_polygon(data = x[chull(x),], alpha = 0.1) +
  geom_polygon(data = hull_of_subset, alpha = 0.3) +
  geom_point(data = centre_point, colour = "green", size = 3)

在此处输入图像描述

我想要一个geom_manythings替换geom_*上面代码中的三个。

在尝试制作自定义几何图形时，我从模板中的代码开始，geom_tufteboxplot以及geom_boxplot“扩展 ggplot2”小插图：

library(ggplot2)
library(proto)

GeomManythings <- ggproto(
  "GeomManythings",
  GeomPolygon,
  setup_data = function(self, data, params) {
    data <- ggproto_parent(GeomPolygon, self)$setup_data(data, params)
    data
  },

  draw_group = function(data, panel_scales, coord) {
    n <- nrow(data)
    if (n <= 2)
      return(grid::nullGrob())

    common <- data.frame(
      colour = data$colour,
      size = data$size,
      linetype = data$linetype,
      fill = alpha(data$fill, data$alpha),
      group = data$group,
      stringsAsFactors = FALSE
    )

    # custom bits...

    # polygon hull for all points
    hull <-  data[chull(data), ]
    hull_df <- data.frame(x = hull$x, 
                          y = hull$y, 
                          common, 
                          stringsAsFactors = FALSE)
    hull_grob <-
      GeomPolygon$draw_panel(hull_df, panel_scales, coord)

    # polygon hull for subset
    subset_of_x <-
      data[data$x > 0 & data$y > 0 ,]
    hull_of_subset <-
      subset_of_x[chull(subset_of_x),]
    hull_of_subset_df <- data.frame(x = hull_of_subset$x, 
                                    y = hull_of_subset$y, 
                                    common, 
                                    stringsAsFactors = FALSE)
    hull_of_subset_grob <-
      GeomPolygon$draw_panel(hull_of_subset_df, panel_scales, coord)

    # point for centre point
    centre_point <-
      data.frame(x = mean(coords$x), 
                 y = coords(data$y),
                 common, 
                 stringsAsFactors = FALSE)

    centre_point_grob <-
      GeomPoint$draw_panel(centre_point, panel_scales, coord)

    # end of custom bits

    ggname("geom_mypolygon",
           grobTree(hull_grob,
                    hull_of_subset_grob,
                    centre_point_grob))


  },

  required_aes = c("x", "y"),

  draw_key = draw_key_polygon,

  default_aes = aes(
    colour = "grey20",
    fill = "grey20",
    size = 0.5,
    linetype = 1,
    alpha = 1,
  )
)

geom_manythings <-
  function(mapping = NULL,
           data = NULL,
           stat = "identity",
           position = "identity",
           na.rm = FALSE,
           show.legend = NA,
           inherit.aes = TRUE,
           ...) {
    layer(
      geom = GeomManythings,
      mapping = mapping,
      data = data,
      stat = stat,
      position = position,
      show.legend = show.legend,
      inherit.aes = inherit.aes,
      params = list(na.rm = na.rm, ...)
    )
  }

但很明显，这个几何中有很多东西不正确，我一定遗漏了一些基本细节...... 

ggplot(x, aes(x, y)) +
  geom_point() +
  geom_manythings()

在此处输入图像描述

我怎样才能写这个geom来得到想要的结果？

4

1 回答 1

9

您的代码中有很多问题，所以我建议您先尝试一个简化的案例。特别是，chull 计算是有问题的。尝试这个，

library(ggplot2)
library(proto)
library(grid)

GeomManythings <- ggproto(
  "GeomManythings",
  Geom,
  setup_data = function(self, data, params) {
    data <- ggproto_parent(Geom, self)$setup_data(data, params)
    data
  },

  draw_group = function(data, panel_scales, coord) {
    n <- nrow(data)
    if (n <= 2)
      return(grid::nullGrob())


    # polygon hull for all points
    hull_df <-  data[chull(data[,c("x", "y")]), ]

    hull_grob <-
      GeomPolygon$draw_panel(hull_df, panel_scales, coord)

    # polygon hull for subset
    subset_of_x <-
      data[data$x > 0 & data$y > 0 ,]
    hull_of_subset_df <-subset_of_x[chull(subset_of_x[,c("x", "y")]),]
    hull_of_subset_df$fill <- "red" # testing
    hull_of_subset_grob <-  GeomPolygon$draw_panel(hull_of_subset_df, panel_scales, coord)

    coords <- coord$transform(data, panel_scales)     

    pg <- pointsGrob(x=mean(coords$x), y=mean(coords$y), 
                     default.units = "npc", gp=gpar(col="green", cex=3))

    ggplot2:::ggname("geom_mypolygon",
                     grobTree(hull_grob,
                              hull_of_subset_grob, pg))


  },


  required_aes = c("x", "y"),

  draw_key = draw_key_polygon,

  default_aes = aes(
    colour = "grey20",
    fill = "grey50",
    size = 0.5,
    linetype = 1,
    alpha = 0.5
  )
)

geom_manythings <-
  function(mapping = NULL,
           data = NULL,
           stat = "identity",
           position = "identity",
           na.rm = FALSE,
           show.legend = NA,
           inherit.aes = TRUE,
           ...) {
    layer(
      geom = GeomManythings,
      mapping = mapping,
      data = data,
      stat = stat,
      position = position,
      show.legend = show.legend,
      inherit.aes = inherit.aes,
      params = list(na.rm = na.rm, ...)
    )
  }


set.seed(9)
n <- 20
d <- data.frame(x = rnorm(n),
                y = rnorm(n))

ggplot(d, aes(x, y)) +
  geom_manythings()+
  geom_point()

在此处输入图像描述

（免责声明：我已经 5 年没有尝试写过 geom，所以我不知道它现在是如何工作的）

于 2016-03-22T19:51:32.063 回答