Question

标题很好地涵盖了它。

我有两个与尺寸和颜色有关的传说，并且希望在图表的顶部和图片中有一个。

这是否可行，如果可行，

TIA

Answer 1

可以通过从图中提取单独的图例，然后在相关图中排列图例来完成。这里的代码使用gtable包中的函数进行提取，然后使用gridExtra包中的函数进行排列。目的是绘制包含颜色图例和尺寸图例的图表。首先，从仅包含颜色图例的图中提取颜色图例。其次，从仅包含尺寸图例的图表中提取尺寸图例。第三，绘制一个不包含图例的情节。第四，将情节和两个传说安排在一个新的情节中。

# Some data
df <- data.frame(
  x = 1:10,
  y = 1:10,
  colour = factor(sample(1:3, 10, replace = TRUE)),
  size = factor(sample(1:3, 10, replace = TRUE)))

library(ggplot2)
library(gridExtra)
library(gtable)
library(grid)

    ### Step 1
# Draw a plot with the colour legend
(p1 <- ggplot(data = df, aes(x=x, y=y)) +
   geom_point(aes(colour = colour)) +
   theme_bw() +
   theme(legend.position = "top"))

# Extract the colour legend - leg1
leg1 <- gtable_filter(ggplot_gtable(ggplot_build(p1)), "guide-box") 

    ### Step 2
# Draw a plot with the size legend
(p2 <- ggplot(data = df, aes(x=x, y=y)) +
   geom_point(aes(size = size)) +
   theme_bw())

# Extract the size legend - leg2
leg2 <- gtable_filter(ggplot_gtable(ggplot_build(p2)), "guide-box") 

    # Step 3
# Draw a plot with no legends - plot
(plot <- ggplot(data = df, aes(x=x, y=y)) +
   geom_point(aes(size = size, colour = colour)) +
   theme_bw() +
   theme(legend.position = "none"))

    ### Step 4
# Arrange the three components (plot, leg1, leg2)
# The two legends are positioned outside the plot: 
# one at the top and the other to the side.
plotNew <- arrangeGrob(leg1, plot, 
         heights = unit.c(leg1$height, unit(1, "npc") - leg1$height), ncol = 1)

plotNew <- arrangeGrob(plotNew, leg2,
          widths = unit.c(unit(1, "npc") - leg2$width, leg2$width), nrow = 1)

grid.newpage()
grid.draw(plotNew)

# OR, arrange one legend at the top and the other inside the plot.
plotNew <- plot + 
        annotation_custom(grob = leg2, xmin = 7, xmax = 10, ymin = 0, ymax = 4)

plotNew <- arrangeGrob(leg1, plotNew,
     heights = unit.c(leg1$height, unit(1, "npc") -  leg1$height), ncol = 1)

grid.newpage()
grid.draw(plotNew)

enter image description here

Answer 2

以下是使用ggplot2和cowplot（= ggplot2扩展名）包的另一种解决方案。

该方法类似于Sandys，因为它将图例作为单独的对象取出，并允许您单独进行放置。它主要设计用于多个图例，这些图例属于图形网格中的两个或多个图。

使用herby的函数g_legend取自answer。

这个想法如下：

创建Plot1，Plot2，...，PlotX 不带图例
使用图例创建Plot1，Plot2，...，PlotX

将第2步中的图例提取为单独的对象

设置图例网格并按照您想要的方式排列图例

创建合并图表和图例的网格

它似乎有点复杂，时间/代码消耗但是设置一次，你可以适应并用于各种情节/图例定制。

library(ggplot2) library(cowplot) # set up function g_legend<-function(a.gplot){ tmp <- ggplot_gtable(ggplot_build(a.gplot)) leg <- which(sapply(tmp$grobs, function(x) x$name) == "guide-box") legend <- tmp$grobs[[leg]] return(legend) } # Some data df <- data.frame( Name = factor(rep(c("A", "B", "C"), 12)), Month = factor(rep(1:12, each=3)), Temp = sample(0:40, 12), Precip = sample(50:400, 12)) # create plot1 plot1 <- ggplot(df, aes(Month, Temp, fill = Name)) + geom_point(show.legend = F, aes(group = Name, colour = Name), size = 3, shape = 17) + geom_smooth(method = "loess", se = F, aes(group = Name, colour = Name), show.legend = F, size = 0.5, linetype = "dashed") # create plot2 plot2 <- ggplot(df, aes(Month, Precip, fill = Name)) + geom_bar(stat = "identity", position = "dodge", show.legend = F) + geom_smooth(method = "loess", se = F, aes(group = Name, colour = Name), show.legend = F, size = 1, linetype = "dashed") + scale_fill_grey() # create legend1 legend1 <- ggplot(df, aes(Month, Temp)) + geom_point(show.legend = T, aes(group = Name, colour = Name), size = 3, shape = 17) + geom_smooth(method = "loess", se = F,aes(group = Name, colour = Name), show.legend = T, size = 0.5, linetype = "dashed") + labs(colour = "Station") + theme(legend.text=element_text(size=8), legend.title = element_text(face = "italic", angle = -0, size = 10)) # create legend2 legend2 <- ggplot(df, aes(Month, Precip, fill = Name)) + geom_bar(stat = "identity", position = "dodge", show.legend = T) + scale_fill_grey() + guides(fill = guide_legend(title = "", title.theme = element_text(face = "italic", angle = -0, size = 10))) + theme(legend.text=element_text(size=8)) # extract "legends only" from ggplot object legend1 <- g_legend(legend1) legend2 <- g_legend(legend2) # setup legends grid legend1_grid <- cowplot::plot_grid(legend1, align = "v", nrow = 2) # add second legend to grid, specifying its location legends <- legend1_grid + ggplot2::annotation_custom(grob = legend2, xmin = 0.5, xmax = 0.5, ymin = 0.55, ymax = 0.55) # plot "plots" + "legends" (with legends in between plots) cowplot::plot_grid(plot1, legends, plot2, ncol = 3, rel_widths = c(0.45, 0.1, 0.45))

<强>示例：

Example http://i65.tinypic.com/jl1lef.png

更改最终plot_grid()调用的顺序会将图例移到右侧：

cowplot::plot_grid(plot1, plot2, legends, ncol = 3, rel_widths = c(0.45, 0.45, 0.1))

Example2 http://i68.tinypic.com/314yn9i.png

Answer 3

根据我的理解，ggplot2基本上对传说的控制非常有限。这是Hadley的书（第111页）中的一段：

ggplot2尝试使用尽可能少的图例来准确传达绘图中使用的美学。如果变量与多个美学一起使用，它可以通过组合图例来实现。图6.14显示了点geom的一个示例：如果颜色和形状都映射到同一个变量，则只需要一个图例。为了合并图例，它们必须具有相同的名称（相同的图例标题）。因此，如果您更改其中一个合并图例的名称，则需要针对所有这些图例进行更改。

如何在ggplot中独立定位两个图例

3 个答案: