r - ggplot2 在绘图区域外添加小刻度线而不关闭剪辑

Question

我正在寻找一种在不使用 coord_cartesian(clip = "off") 的情况下向 ggplots 添加小刻度线的方法.或者一种可重现的方式将裁剪应用到 x 轴而不是 y 轴，反之亦然。

到目前为止，我一直在使用 annotation_ticks()函数和 GeomTicks geom 在这个优秀的答案中定义 here (稍作修改以使其与 ggplot2 v3.3.0 一起使用)。不幸的是，要使刻度线注释出现在绘图的外部，必须使用 coord_cartesian(clip = "off")这意味着位于绘图区域之外的任何其他东西也会被暴露(参见下面的 reprex)。

或者，也许有一种方法可以利用 ggplot2 v3.3.0 的任何新功能。绘制小刻度不是作为注释而是作为轴/绘图的实际部分，以便可以将它们绘制在绘图区域之外。

我不是软件开发人员，但也许可以使用 register_theme_elements 定义一个新的主题元素。叫 axis.minor.ticks行为类似于 axis.ticks但从 panel_params$y$break_positions_minor 获取次要刻度的适当位置而不是 panel_params$y$break_positions .或者以某种方式使用新的 guide_x() S3 功能。

任何帮助将非常感激!

注解函数和ggproto对象
annotation_ticks()功能(包含 this fix 用于刻面问题):

annotation_ticks <- function(sides = "b",
                             scale = "identity",
                             scaled = TRUE,
                             ticklength = unit(0.1, "cm"),
                             colour = "black",
                             size = 0.5,
                             linetype = 1,
                             alpha = 1,
                             color = NULL,
                             ticks_per_base = NULL,
                             data = data.frame(x = NA), 
                             ...) {
  if (!is.null(color)) {
    colour <- color
  }

  # check for invalid side
  if (grepl("[^btlr]", sides)) {
    stop(gsub("[btlr]", "", sides), " is not a valid side: b,t,l,r are valid")
  }

  # split sides to character vector
  sides <- strsplit(sides, "")[[1]]

  if (length(sides) != length(scale)) {
    if (length(scale) == 1) {
      scale <- rep(scale, length(sides))
    } else {
      stop("Number of scales does not match the number of sides")
    }
  }

  base <- sapply(scale, function(x) switch(x, "identity" = 10, "log10" = 10, "log" = exp(1)), USE.NAMES = FALSE)

  if (missing(ticks_per_base)) {
    ticks_per_base <- base - 1
  } else {
    if ((length(sides) != length(ticks_per_base))) {
      if (length(ticks_per_base) == 1) {
        ticks_per_base <- rep(ticks_per_base, length(sides))
      } else {
        stop("Number of ticks_per_base does not match the number of sides")
      }
    }
  }

  delog <- scale %in% "identity"

  layer(
    data = data,
    mapping = NULL,
    stat = StatIdentity,
    geom = GeomTicks,
    position = PositionIdentity,
    show.legend = FALSE,
    inherit.aes = FALSE,
    params = list(
      base = base,
      sides = sides,
      scaled = scaled,
      ticklength = ticklength,
      colour = colour,
      size = size,
      linetype = linetype,
      alpha = alpha,
      ticks_per_base = ticks_per_base,
      delog = delog,
      ...
    )
  )
}

ggproto 对象(现在与 ggplot2 v3.3.0 一起使用):

GeomTicks <- ggproto(
  "GeomTicks", Geom,
  extra_params = "",
  handle_na = function(data, params) {
    data
  },

  draw_panel = function(data,
                        panel_scales,
                        coord,
                        base = c(10, 10),
                        sides = c("b", "l"),
                        scaled = TRUE,
                        ticklength = unit(0.1, "cm"),
                        ticks_per_base = base - 1,
                        delog = c(x = TRUE, y = TRUE)) {
    ticks <- list()

    for (s in 1:length(sides)) {
      if (grepl("[b|t]", sides[s])) {

        # for ggplot2 < 3.3.0 use: xticks <- panel_params$x.minor
        if (utils::packageVersion("ggplot2") >= "3.2.1.9000") {
          x_minor_breaks <- panel_scales$x$break_positions_minor()
          x_major_breaks <- panel_scales$x$break_positions()
        } else {
          x_minor_breaks <- panel_scales$x.minor
          x_major_breaks <- panel_scales$x.major
        }

        xticks <- setdiff(x_minor_breaks, x_major_breaks)

        # Make the grobs
        if (grepl("b", sides[s])) {
          ticks$x_b <- with(
            data,
            segmentsGrob(
              x0 = unit(xticks, "npc"),
              x1 = unit(xticks, "npc"),
              y0 = unit(0, "npc"),
              y1 = ticklength,
              gp = gpar(
                col = alpha(colour, alpha),
                lty = linetype,
                lwd = size * .pt
              )
            )
          )
        }
        if (grepl("t", sides[s])) {
          ticks$x_t <- with(
            data,
            segmentsGrob(
              x0 = unit(xticks, "npc"),
              x1 = unit(xticks, "npc"),
              y0 = unit(1, "npc"),
              y1 = unit(1, "npc") - ticklength,
              gp = gpar(
                col = alpha(colour, alpha),
                lty = linetype,
                lwd = size * .pt
              )
            )
          )
        }
      }


      if (grepl("[l|r]", sides[s])) {

        # for ggplot2 < 3.3.0 use: yticks <- panel_params$y.minor
        if (utils::packageVersion("ggplot2") >= "3.2.1.9000") {
          y_minor_breaks <- panel_scales$y$break_positions_minor()
          y_major_breaks <- panel_scales$y$break_positions()
        } else {
          y_minor_breaks <- panel_scales$y.minor
          y_major_breaks <- panel_scales$y.major
        }

        yticks <- setdiff(y_minor_breaks, y_major_breaks)

        # Make the grobs
        if (grepl("l", sides[s])) {
          ticks$y_l <- with(
            data,
            segmentsGrob(
              y0 = unit(yticks, "npc"),
              y1 = unit(yticks, "npc"),
              x0 = unit(0, "npc"),
              x1 = ticklength,
              gp = gpar(
                col = alpha(colour, alpha),
                lty = linetype, lwd = size * .pt
              )
            )
          )
        }
        if (grepl("r", sides[s])) {
          ticks$y_r <- with(
            data,
            segmentsGrob(
              y0 = unit(yticks, "npc"),
              y1 = unit(yticks, "npc"),
              x0 = unit(1, "npc"),
              x1 = unit(1, "npc") - ticklength,
              gp = gpar(
                col = alpha(colour, alpha),
                lty = linetype,
                lwd = size * .pt
              )
            )
          )
        }
      }
    }
    gTree(children = do.call("gList", ticks))
  },
  default_aes = aes(colour = "black", size = 0.5, linetype = 1, alpha = 1)
)

图形与 coord_cartesian(clip = "on")
线宽很粗的列看起来不错，但看不到刻度注释。

library(ggplot2)
library(grid)

ggplot(mpg, aes(x = class, y = displ, fill = class)) + 
  stat_summary(fun = mean, geom = "col", colour = "black", size = 1) + 
  theme_classic(base_size = 8) + 
  scale_y_continuous(limits = c(0, 8), expand = c(0, 0)) + 
  annotation_ticks(sides = "l", ticklength = -1 * unit(0.2, "cm")) + 
  coord_cartesian(clip = "on")

ggsave("clip_on.png", device = "png", width = 4, height = 3)

column plot with clip=on

图形与 coord_cartesian(clip = "off")
刻度注释可见，但线宽非常粗的列显示在绘图区域之外。

ggplot(mpg, aes(x = class, y = displ, fill = class)) + 
  stat_summary(fun = mean, geom = "col", colour = "black", size = 1) + 
  theme_classic(base_size = 8) + 
  scale_y_continuous(limits = c(0, 8), expand = c(0, 0)) + 
  annotation_ticks(sides = "l", ticklength = -1 * unit(0.2, "cm")) + 
  coord_cartesian(clip = "off")

ggsave("clip_off.png", device = "png", width = 4, height = 3)

column plot with clip=off

Answer 1

这段代码对我来说似乎很熟悉，所以我想权衡一下。

是的，使用 ggplot v3.3.0 指南已经变得可扩展，尽管我怀疑它们会在很长一段时间内保持当前的形式，因为通过小道消息我听说他们也想将指南切换到 ggproto 系统。

没有太多花里胡哨的方法来做你所要求的最便宜的方法是调整指南的指南培训部分。由于这是一个 S3 方法，我们需要一个新的指南类来编写自定义方法:

library(ggplot2)
library(rlang)
#> Warning: package 'rlang' was built under R version 3.6.3
library(glue)

guide_axis_minor <- function(
  title = waiver(), check.overlap = FALSE, angle = NULL,
  n.dodge = 1, order = 0, position = waiver()
) {
  structure(list(title = title, check.overlap = check.overlap, 
                 angle = angle, n.dodge = n.dodge, order = order, position = position, 
                 available_aes = c("x", "y"), name = "axis"), 
            class = c("guide", "axis_minor", "axis"))
}

您会注意到上面的函数与 guide_axis() 相同，除了一个额外的类。类的顺序在这里很重要，因为我们正在继承 axis类，这样我们就可以偷懒，只使用所有已经存在的方法。

这将我们带到了训练中，这确实是唯一需要稍微调整的东西。我已经在相关位中发表了评论。大部分功能仍与 guide_train.axis 相同内部功能。简而言之，我们将小中断视为带有空标签的主要中断。

guide_train.axis_minor <- function(guide, scale, aesthetic = NULL) {
  aesthetic <- aesthetic %||% scale$aesthetics[1]

  # Seperately define major and minor breaks
  major_breaks <- scale$get_breaks()
  minor_breaks <- scale$get_breaks_minor()

  # We set the actual breaks to be both major and minor
  breaks <- union(major_breaks, minor_breaks)

  # We keep track of what breaks were the major breaks
  is_major <- breaks %in% major_breaks

  empty_ticks <- ggplot2:::new_data_frame(
    list(aesthetic = numeric(), .value = numeric(0), .label = character())
  )
  if (length(intersect(scale$aesthetics, guide$available_aes)) == 0) {
    warn(glue("axis guide needs appropriate scales: ", 
              glue_collapse(guide$available_aes, ", ", last = " or ")))
    guide$key <- empty_ticks
  } else if (length(breaks) == 0) {
    guide$key <- empty_ticks
  } else {
    mapped_breaks <- if (scale$is_discrete()) {
      scale$map(breaks)
    } else {
      breaks
    }
    ticks <- ggplot2:::new_data_frame(setNames(list(mapped_breaks), 
                                     aesthetic))
    ticks$.value <- breaks
    ticks$.label <- scale$get_labels(breaks)

    # Now this is the bit where we set minor breaks to have empty labls
    ticks$.label[!is_major] <- ""

    guide$key <- ticks[is.finite(ticks[[aesthetic]]), ]
  }
  guide$name <- paste0(guide$name, "_", aesthetic)
  guide$hash <- digest::digest(list(guide$title, guide$key$.value, 
                                    guide$key$.label, guide$name))
  guide
}

然后，因为我们子类化了 axis类，为该类编写的所有函数也适用于我们的 axis_minor类，所以我们完成了。现在，您可以按名称从任何连续位置比例调用指南:

ggplot(mpg, aes(x = class, y = displ, fill = class)) + 
  stat_summary(fun = mean, geom = "col") + 
  scale_y_continuous(limits = c(0, 8), 
                     guide = "axis_minor")

创建于 2020-04-07 由 reprex package (v0.3.0)