创建一个多列分面函数

12
我正在尝试创建一个facet_multi_col()函数,类似于ggforce中的facet_col()函数 - 它允许使用空间参数(在facet_wrap()中不可用)进行面板布局 - 但是可以跨多列。就像下面的最后一个图(使用grid.arrange()创建)一样,我不希望各个面板必须在行上对齐,因为每个面板中的高度将根据我想要使用的分类y变量而异。

我发现自己在阅读扩展guide后已经超出了我的能力范围,其中包括ggproto。我认为最好的方法是传递一个布局矩阵来指示在相应的数据子集中何时断开列,并基于facet_col在 ggforce 中构建一个包含空间参数的函数 - 请参见问题结尾。

我不满意的选项的快速说明

没有面板

library(tidyverse)
library(gapminder)
global_tile <- ggplot(data = gapminder, mapping = aes(x = year, y = fct_rev(country), fill = lifeExp)) +
  geom_tile()
global_tile

输入图像描述 我想按大洲分类分解情节,但不想要这么长的图。

facet_wrap()

global_tile +
  facet_wrap(facets = "continent", scales = "free")

enter image description here facet_wrap()没有空间参数,这意味着每个大陆的图块大小不同,使用coord_equal()会引发错误。

ggforce中的facet_col()

library(ggforce)
global_tile +
  facet_col(facets = "continent", scales = "free", space = "free", strip.position = "right") +
  theme(strip.text.y = element_text(angle = 0)) 

这里输入图片描述 喜欢侧面的条纹。 space 参数将所有瓷砖设置为相同的大小。 仍然太长无法适合页面。

gridExtra中的grid.arrange()

为每个大陆应放置的位置添加一个列列

d <- gapminder %>%
  as_tibble() %>%
  mutate(col = as.numeric(continent), 
         col = ifelse(test = continent == "Europe", yes = 2, no = col),
         col = ifelse(test = continent == "Oceania", yes = 3, no = col))
head(d)
# # A tibble: 6 x 7
#   country     continent  year lifeExp      pop gdpPercap   col
#   <fct>       <fct>     <int>   <dbl>    <int>     <dbl> <dbl>
# 1 Afghanistan Asia       1952    28.8  8425333      779.     3
# 2 Afghanistan Asia       1957    30.3  9240934      821.     3
# 3 Afghanistan Asia       1962    32.0 10267083      853.     3
# 4 Afghanistan Asia       1967    34.0 11537966      836.     3
# 5 Afghanistan Asia       1972    36.1 13079460      740.     3
# 6 Afghanistan Asia       1977    38.4 14880372      786.     3
tail(d)
# # A tibble: 6 x 7
#   country  continent  year lifeExp      pop gdpPercap   col
#   <fct>    <fct>     <int>   <dbl>    <int>     <dbl> <dbl>
# 1 Zimbabwe Africa     1982    60.4  7636524      789.     1
# 2 Zimbabwe Africa     1987    62.4  9216418      706.     1
# 3 Zimbabwe Africa     1992    60.4 10704340      693.     1
# 4 Zimbabwe Africa     1997    46.8 11404948      792.     1
# 5 Zimbabwe Africa     2002    40.0 11926563      672.     1
# 6 Zimbabwe Africa     2007    43.5 12311143      470.     1

使用facet_col()函数为每一列绘制图表。
g <- list()
for(i in unique(d$col)){
  g[[i]] <- d %>%
    filter(col == i) %>%
    ggplot(mapping = aes(x = year, y = fct_rev(country), fill = lifeExp)) +
    geom_tile() +
    facet_col(facets = "continent", scales = "free_y", space = "free", strip.position = "right") +
    theme(strip.text.y = element_text(angle = 0)) +
    # aviod legends in every column
    guides(fill = FALSE) +
    labs(x = "", y = "")
}

使用cowplot中的get_legend()创建图例。
library(cowplot)
gg <- ggplot(data = d, mapping = aes(x = year, y = country, fill = lifeExp)) +
  geom_tile()
leg <- get_legend(gg)

创建一个布局矩阵,其高度基于每列中国家的数量。
m <- 
  d %>%
  group_by(col) %>%
  summarise(row = n_distinct(country)) %>%
  rowwise() %>%
  mutate(row = paste(1:row, collapse = ",")) %>%
  separate_rows(row) %>%
  mutate(row = as.numeric(row), 
         col = col, 
         p = col) %>% 
  xtabs(formula = p ~ row + col) %>%
  cbind(max(d$col) + 1) %>%
  ifelse(. == 0, NA, .)

head(m)
#   1 2 3  
# 1 1 2 3 4
# 2 1 2 3 4
# 3 1 2 3 4
# 4 1 2 3 4
# 5 1 2 3 4
# 6 1 2 3 4

tail(m)
#     1 2  3  
# 50  1 2 NA 4
# 51  1 2 NA 4
# 52  1 2 NA 4
# 53 NA 2 NA 4
# 54 NA 2 NA 4
# 55 NA 2 NA 4

gridExtra中使用grid.arrange()gleg组合在一起。

library(gridExtra)
grid.arrange(g[[1]], g[[2]], g[[3]], leg, layout_matrix = m, widths=c(0.32, 0.32, 0.32, 0.06))

enter image description here 这几乎是我想要的,但我不满意的是a)不同列中的瓷砖具有不同的宽度,因为最长的国家和大陆名称的长度不相等;b)这是一堆需要调整的代码,每次我想制作这样的图时都需要进行调整 - 对于其他数据,我想按区域排列外观,例如“西欧”,而不是大陆或国家数量发生变化 - 在gapminder数据中没有中亚国家。

创建facet_multi_cols()函数的进展

我想将布局矩阵传递给facet函数,其中矩阵将引用每个facet,并且函数可以根据每个面板中空格数来确定高度。对于上面的示例,矩阵将为:

my_layout <- matrix(c(1, NA, 2, 3, 4, 5), nrow = 2)
my_layout
#      [,1] [,2] [,3]
# [1,]    1    2    4
# [2,]   NA    3    5

如上所述,我一直在适应facet_col()中的代码,以尝试构建一个facet_multi_col()函数。我添加了一个layout参数来提供类似于上面的my_layout的矩阵,其想法是,例如,将给定给facets参数的变量的第四和第五级绘制在第三列中。
facet_multi_col <- function(facets, layout, scales = "fixed", space = "fixed",
                      shrink = TRUE, labeller = "label_value",
                      drop = TRUE, strip.position = 'top') {
  # add space argument as in facet_col
  space <- match.arg(space, c('free', 'fixed'))
  facet <- facet_wrap(facets, col = col, dir = dir, scales = scales, shrink = shrink, labeller = labeller, drop = drop, strip.position = strip.position)
  params <- facet$params
  params <- facet$layout

  params$space_free <- space == 'free'
  ggproto(NULL, FacetMultiCols, shrink = shrink, params = params)
}

FacetMultiCols <- ggproto('FacetMultiCols', FacetWrap,
  # from FacetCols to allow for space argument to work
  draw_panels = function(self, panels, layout, x_scales, y_scales, ranges, coord, data, theme, params) {
    combined <- ggproto_parent(FacetWrap, self)$draw_panels(panels, layout, x_scales, y_scales, ranges, coord, data, theme, params)
    if (params$space_free) {
      widths <- vapply(layout$PANEL, function(i) diff(ranges[[i]]$x.range), numeric(1))
      panel_widths <- unit(widths, "null")
      combined$widths[panel_cols(combined)$l] <- panel_widths
    }
    combined
  }
  # adapt FacetWrap layout to set position on panels following the matrix given to layout in facet_multi_col().
  compute_layout = function(self, panels, layout, x_scales, y_scales, ranges, coord, data, theme, params) {
    layout <- ggproto_parent(FacetWrap, self)$compute_layout(panels, layout, x_scales, y_scales, ranges, coord, data, theme, params)
    # ???
)

我认为我需要为compute_layout部分编写一些内容,但我很难想出如何做到这一点。


你尝试过制作一个包含每个大陆的绘图列表,并使用 cowplot 或 patchwork 等软件包对它们进行对齐吗?这可能比构建 ggproto 更容易。 - camille
@camille 我有点做了...就在上面的grid.arrange示例中..除非你指的是不同的东西?我认为在每列中使用不同的标签长度会存在相同的问题。 - guyabel
我想象着类似的东西,但是那些布局包可能比 grid.arrange 更好地帮助对齐。这是一篇非常长的文章,所以很难跟上你尝试的所有内容。有点 hacky,但你可以尝试使用等宽字体/更加均匀间距的标签,以便它们的长度更可预测。你甚至可以用空格填充标签,以确保文本更接近相同的长度。 - camille
2个回答

6

免责声明

我从未开发过facet,但我觉得这个问题很有趣且具有挑战性,所以我尝试了一下。它还不完美,也没有测试过所有可能出现的细微差别,取决于您的情节,但这是一个初步草案,您可以在此基础上继续工作。

思路

facet_wrap将面板设置在表格中,每行都有一定的高度,其中面板完全占用。 gtable_add_grob说:

在gtable模型中,grobs始终填满完整的表格单元格。如果您想要自定义对齐方式,可能需要在绝对单位中定义grob尺寸,或将其放入另一个gtable中,然后将其添加到gtable而不是grob中。

可能是一个有趣的解决方案。 但是,我不确定如何继续。 因此,我采取了不同的方法:

  1. 创建一个基于传递的布局参数的自定义布局
  2. facet_wrap按照布局渲染所有面板
  3. 使用gtable_filter获取包括其轴和条带在内的面板
  4. 创建布局矩阵。 我尝试了2种方法:使用最少数量的行并玩弄高度差异。 以及仅添加大约与y轴上的刻度数相同数量的行。 这两者都可以运作,但后者生成的代码更清晰,因此我会使用这个。
  5. 使用gridExtra :: arrangeGrob根据传递的设计和创建的布局矩阵排列面板

结果

完整的代码有点长,但可以在下面找到。 这里有一些图形:

my_layout1 <- matrix(c(1, NA, 2, 3, 4, 5), nrow = 2)
my_layout2 <- matrix(c(1, 2, 3, 4, 5, NA), ncol = 2)

## Ex1
global_tile + facet_multi_col("continent", my_layout1, scales = "free_y", 
                              space = "free", strip.position = "top")

## Ex 2
global_tile + facet_multi_col("continent", my_layout1, scales = "free_y", 
                              space = "free", strip.position = "right")

## Ex 3 - shows that we need a minimum space for any plot 
global_tile + facet_multi_col("continent", my_layout1, scales = "free_y", 
                              space = "free", strip.position = "top", min_prop = 0)

## Ex 4
global_tile + facet_multi_col("continent", my_layout1, scales = "free_y", 
                              space = "fixed", strip.position = "right")

## Ex 5
global_tile + facet_multi_col("continent", my_layout2, scales = "free_y", 
                              space = "free")

示例1 Example 1 示例2 Example 2 示例3 Example 3 示例4 Example 4 示例5 Example 5

限制

该代码远非万无一失。我已经发现了一些问题:

  • 我们(暗地里)假设设计中每个列都以非 NA 值开头(通常情况下,为了编写高效的代码,需要仔细检查传递的布局是否合适(尺寸是否合适?面板数量是否正确等)。
  • 非常小的面板无法呈现得很好,因此我不得不根据条带的位置为高度添加最小值。
  • 移动或添加轴或条带的效果尚未测试。

代码:每个刻度一行

## get strip and axis of a given panel
## Assumptions:
## - axis are adjacent to the panel, that is exactly +1/-1 positions to the t/b/l/r ...
## - ... unless there is a strip then it is +2/-2 
get_whole_panel <- function(panel_name,
                            table_layout) {
  target <- table_layout$layout %>%
    dplyr::filter(name == panel_name) %>%
    dplyr::select(row = t, col = l)
  stopifnot(NROW(target) == 1)
  pos <- unlist(target)
  dirs <- list(t = c(-1, 0),
               b = c(1, 0),
               l = c(0, -1),
               r = c(0, 1))
  filter_elems <- function(dir, 
                           type = c("axis", "strip")) {
    type <- match.arg(type)
    new_pos <- pos + dir
    res <- table_layout$layout %>%
      dplyr::filter(grepl(type, name),
                    l == new_pos["col"],
                    t == new_pos["row"]) %>%
      dplyr::pull(name)
    if (length(res)) res else NA
  }
  strip <- purrr::map_chr(dirs, filter_elems, type = "strip")
  strip <- strip[!is.na(strip)]
  dirs[[names(strip)]] <- 2 * dirs[[names(strip)]]
  axes  <- purrr::map_chr(dirs, filter_elems, type = "axis")
  gtable::gtable_filter(table_layout, paste(c(panel_name, axes, strip), collapse = "|"))
}


facet_multi_col <- function(facets, layout, scales = "fixed", space = "fixed",
                            shrink = TRUE, labeller = "label_value",
                            drop = TRUE, strip.position = "top", 
                            min_prop = ifelse(strip.position %in% c("top", "bottom"), 
                                              0.12, 0.1)) {
  space <- match.arg(space, c("free", "fixed"))
  if (space == "free") {
    ## if we ask for free space we need scales everywhere, so make sure they are included
    scales <- "free"
  }
  facet <- facet_wrap(facets, ncol = 1, scales = scales, shrink = shrink, 
                      labeller = labeller, drop = drop, strip.position = strip.position)
  params <- facet$params
  params$space_free <- space == "free"
  params$layout <- layout
  params$parent <- facet
  params$min_prop <- min_prop
  ggproto(NULL, FacetMultiCol, shrink = shrink, params = params)
}



render <- function(self, panels, layout, 
                   x_scales, y_scales, ranges, 
                   coord, data, theme, params) {
  combined <- ggproto_parent(FacetWrap, self)$draw_panels(panels, layout, 
                                                          x_scales, y_scales, ranges, 
                                                          coord, data, theme, params)
  if (params$space_free) {
    panel_names <- combined$layout$name
    panels <- lapply(panel_names[grepl("panel", panel_names)],
                     get_whole_panel,
                     table_layout = combined)

    ## remove zeroGrob panels
    zG <- sapply(panels, function(tg) all(sapply(tg$grobs, ggplot2:::is.zero)))
    panels <- panels[!zG]
    ## calculate height for each panel
    heights <- matrix(NA, NROW(params$layout), NCOL(params$layout))
    ## store the rounded range in the matrix cell corresponding to its position
    ## allow for a minimum space in dependence of the overall number of rows to
    ## render small panels well

    heights[as.matrix(layout[, c("ROW", "COL")])] <- vapply(ranges, function(r) 
      round(diff(r$y.range), 0), numeric(1))

    ## 12% should be the minimum height used by any panel if strip is on top otherwise 10%
    ## these values are empirical and can be changed
    min_height <- round(params$min_prop * max(colSums(heights, TRUE)), 0)
    heights[heights < min_height] <- min_height
    idx <- c(heights)
    idx[!is.na(idx)] <- seq_along(idx[!is.na(idx)])
    len_out <- max(colSums(heights, TRUE))
    i <- 0
    layout_matrix <- apply(heights, 2, function(col) {
      res <- unlist(lapply(col, function(n) {
        i <<- i + 1
        mark <- idx[i]
        if (is.na(n)) {
          NA
        } else {
          rep(mark, n)
        }
      }))
      len <- length(res)
      if (len < len_out) {
        res <- c(res, rep(NA, len_out - len))
      }
      res
    })

    ## set width of left axis to maximum width to align plots
    max_width <- max(do.call(grid::unit.c, lapply(panels, function(gt) gt$widths[1])))
    panels <- lapply(panels, function(p) {
      p$widths[1] <- max_width
      p
    })

    combined <- gridExtra::arrangeGrob(grobs = panels,
                            layout_matrix = layout_matrix,
                            as.table = FALSE)
    ## add name, such that find_panel can find the plotting area
    combined$layout$name <- paste("panel_", layout$LAB)
  }
  combined
}

layout <- function(data, params) {
  parent_layout <- params$parent$compute_layout(data, params)
  msg <- paste0("invalid ",
                sQuote("layout"),
                ". Falling back to ",
                sQuote("facet_wrap"),
                " layout")
  if (is.null(params$layout) ||
      !is.matrix(params$layout)) {
    warning(msg)
    parent_layout
  } else {
    ## smash layout into vector and remove NAs all done by sort
    layout <- params$layout
    panel_numbers <- sort(layout)
    if (!isTRUE(all.equal(sort(as.numeric(as.character(parent_layout$PANEL))),
                          panel_numbers))) {
      warning(msg)
      parent_layout
    } else {
      ## all good
      indices <- cbind(ROW = c(row(layout)),
                       COL = c(col(layout)),
                       PANEL = c(layout))
      indices <- indices[!is.na(indices[, "PANEL"]), ]
      ## delete row and col number from parent layout
      parent_layout$ROW <- parent_layout$COL <- NULL
      new_layout <- merge(parent_layout, 
                          indices,
                          by = "PANEL") %>%
        dplyr::arrange(PANEL)
      new_layout$PANEL <- factor(new_layout$PANEL)
      labs <- new_layout %>%
        dplyr::select(-PANEL,
                      -SCALE_X,
                      -SCALE_Y,
                      -ROW,
                      -COL) %>%
        dplyr::mutate(sep = "_") %>%
        do.call(paste, .)
      new_layout$LAB <- labs
      new_layout


    }
  }
}

FacetMultiCol <- ggproto("FacetMultiCol", FacetWrap,
                         compute_layout = layout,
                         draw_panels    = render)

代码:不同高度的行

## get strip and axis of a given panel
## Assumptions:
## - axis are adjacent to the panel, that is exactly +1/-1 positions to the t/b/l/r ...
## - ... unless there is a strip then it is +2/-2 
get_whole_panel <- function(panel_name,
                            table_layout) {
  target <- table_layout$layout %>%
    dplyr::filter(name == panel_name) %>%
    dplyr::select(row = t, col = l)
  stopifnot(NROW(target) == 1)
  pos <- unlist(target)
  dirs <- list(t = c(-1, 0),
               b = c(1, 0),
               l = c(0, -1),
               r = c(0, 1))
  filter_elems <- function(dir, 
                           type = c("axis", "strip")) {
    type <- match.arg(type)
    new_pos <- pos + dir
    res <- table_layout$layout %>%
      dplyr::filter(grepl(type, name),
                    l == new_pos["col"],
                    t == new_pos["row"]) %>%
      dplyr::pull(name)
    if (length(res)) res else NA
  }
  strip <- purrr::map_chr(dirs, filter_elems, type = "strip")
  strip <- strip[!is.na(strip)]
  dirs[[names(strip)]] <- 2 * dirs[[names(strip)]]
  axes  <- purrr::map_chr(dirs, filter_elems, type = "axis")
  gtable::gtable_filter(table_layout, paste(c(panel_name, axes, strip), collapse = "|"))
}


facet_multi_col <- function(facets, layout, scales = "fixed", space = "fixed",
                            shrink = TRUE, labeller = "label_value",
                            drop = TRUE, strip.position = "top") {
  space <- match.arg(space, c("free", "fixed"))
  if (space == "free") {
    ## if we ask for free space we need scales everywhere, so make sure they are included
    scales <- "free"
  }
  facet <- facet_wrap(facets, ncol = 1, scales = scales, shrink = shrink, 
                      labeller = labeller, drop = drop, strip.position = strip.position)
  params <- facet$params
  params$space_free <- space == "free"
  params$layout <- layout
  params$parent <- facet
  ggproto(NULL, FacetMultiCol, shrink = shrink, params = params)
}



render <- function(self, panels, layout, 
                   x_scales, y_scales, ranges, 
                   coord, data, theme, params) {
  combined <- ggproto_parent(FacetWrap, self)$draw_panels(panels, layout, 
                                                          x_scales, y_scales, ranges, 
                                                          coord, data, theme, params)
  if (params$space_free) {
    panel_names <- combined$layout$name
    panels <- lapply(panel_names[grepl("panel", panel_names)],
                     get_whole_panel,
                     table_layout = combined)

    ## remove zeroGrob panels
    zG <- sapply(panels, function(tg) all(sapply(tg$grobs, ggplot2:::is.zero)))
    panels <- panels[!zG]

    ## calculate height for each panel
    heights <- matrix(NA, NROW(params$layout), NCOL(params$layout))
    ## need to add a minimum height as otherwise the space is too narrow
    heights[as.matrix(layout[, c("ROW", "COL")])] <- vapply(layout$PANEL, function(i) 
      max(diff(ranges[[i]]$y.range), 8), numeric(1))
    heights_cum <- sort(unique(unlist(apply(heights, 2, 
                                            function(col) cumsum(col[!is.na(col)])))))
    heights_units <- unit(c(heights_cum[1], diff(heights_cum)), "null")

    ## set width of left axis to maximum width to align plots
    max_width <- max(do.call(grid::unit.c, lapply(panels, function(gt) gt$widths[1])))
    panels <- lapply(panels, function(p) {
      p$widths[1] <- max_width
      p
    })

    mark <- 0

    ## create layout matrix
    layout_matrix <- apply(heights, 2, function(h) {
      idx <- match(cumsum(h),
              cumsum(c(heights_units)))
      idx <- idx[!is.na(idx)]
      res <- unlist(purrr::imap(idx, function(len_out, pos) {
        mark <<- mark + 1
        offset <- if (pos != 1) idx[pos - 1] else 0
          rep(mark, len_out - offset)
      }))
      len_out <- length(res)
      if (len_out < length(heights_units)) {
        res <- c(res, rep(NA, length(heights_units) - len_out)) 
      }
      res
    }) 

    combined <- gridExtra::arrangeGrob(grobs = panels,
                                layout_matrix = layout_matrix,
                                heights = heights_units,
                                as.table = FALSE)
    ## add name, such that find_panel can find the plotting area
    combined$layout$name <- paste("panel_", layout$LAB)
  }
  combined
}

layout <- function(data, params) {
  parent_layout <- params$parent$compute_layout(data, params)
  msg <- paste0("invalid ",
                sQuote("layout"),
                ". Falling back to ",
                sQuote("facet_wrap"),
                " layout")
  if (is.null(params$layout) ||
      !is.matrix(params$layout)) {
    warning(msg)
    parent_layout
  } else {
    ## smash layout into vector and remove NAs all done by sort
    layout <- params$layout
    panel_numbers <- sort(layout)
    if (!isTRUE(all.equal(sort(as.numeric(as.character(parent_layout$PANEL))),
                          panel_numbers))) {
      warning(msg)
      parent_layout
    } else {
      ## all good
      indices <- cbind(ROW = c(row(layout)),
                       COL = c(col(layout)),
                       PANEL = c(layout))
      indices <- indices[!is.na(indices[, "PANEL"]), ]
      ## delete row and col number from parent layout
      parent_layout$ROW <- parent_layout$COL <- NULL
      new_layout <- merge(parent_layout, 
                          indices,
                          by = "PANEL") %>%
        dplyr::arrange(PANEL)
      new_layout$PANEL <- factor(new_layout$PANEL)
      labs <- new_layout %>%
        dplyr::select(-PANEL,
                      -SCALE_X,
                      -SCALE_Y,
                      -ROW,
                      -COL) %>%
        dplyr::mutate(sep = "_") %>%
        do.call(paste, .)
      new_layout$LAB <- labs
      new_layout


    }
  }
}

FacetMultiCol <- ggproto("FacetMultiCol", FacetWrap,
                         compute_layout = layout,
                         draw_panels    = render)

你能分享一下数据的快照吗?我查看了要点,但由于明显的原因无法重现问题... - thothal
啊,抱歉,我的错。我会尝试的。 - thothal
1
发现了一个错误,基本上布局必须按照面板进行排序,否则它将无法工作。你的示例现在可以正常渲染。 - thothal
我已经将绘图图片作为评论上传至您的gist中。 - thothal
谢谢...有没有办法为每一列获取共享的x轴..目前scales = "free_y"不像其他分面函数那样起作用。 - guyabel
显示剩余5条评论

3
如评论中所建议的,cowplot和patchwork的组合可以让你走得相当远。请见下面我的解决方案。
基本思路是:
- 首先计算一个缩放因子,基于行数; - 然后制作一系列单列网格,在其中使用空白图来限制具有计算缩放因子的绘图的高度(并删除图例); - 接着将它们添加到一个网格中,并添加一个图例; - 最开始,我还计算了填充比例的最大值。
library(tidyverse)
library(gapminder)
library(patchwork)
max_life <- max(gapminder$lifeExp)
generate_plot <- function(data, title){
  ggplot(data = data, mapping = aes(x = year, y = fct_rev(country), fill = lifeExp)) +
    geom_tile()+
    scale_fill_continuous(limits = c(0, max_life)) +
    ggtitle(title)
}
scale_plot <- function(plot, ratio){
  plot + theme(legend.position="none") + 
    plot_spacer() + 
    plot_layout(ncol = 1,
                heights = c(
                  ratio,
                  1-ratio
                )
    )
}
df <- gapminder %>% 
  group_by(continent) %>% 
  nest() %>% 
  ungroup() %>% 
  arrange(continent) %>% 
  mutate(
    rows = map_dbl(data, nrow),
    rel_height = (rows/max(rows)),
    plot = map2(
      data,
      continent,
      generate_plot
    ),
    spaced_plot = map2(
      plot,
      rel_height,
      scale_plot
        )
  )
wrap_plots(df$spaced_plot) + cowplot::get_legend(df$plot[[1]])

此文本由reprex package(版本0.3.0)于2019年11月6日创建


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