将共享图例与绘图网格的中心对齐(使用牛皮图)

Question

可重复的示例可以在本教程中找到包牛皮图.

https://cran.r-project.org/web/packages/cowplot/vignettes/shared_legends.html

复制示例代码:

library(ggplot2)
library(cowplot)
#down-sampled diamonds data set
dsamp <- diamonds[sample(nrow(diamonds), 1000), ]

# Make three plots.
# We set left and right margins to 0 to remove unnecessary spacing in the
# final plot arrangement.
p1 <- qplot(carat, price, data=dsamp, colour=clarity) +
  theme(plot.margin = unit(c(6,0,6,0), "pt"))
p2 <- qplot(depth, price, data=dsamp, colour=clarity) +
  theme(plot.margin = unit(c(6,0,6,0), "pt")) + ylab("")
p3 <- qplot(color, price, data=dsamp, colour=clarity) +
  theme(plot.margin = unit(c(6,0,6,0), "pt")) + ylab("")

# arrange the three plots in a single row
prow <- plot_grid( p1 + theme(legend.position="none"),
           p2 + theme(legend.position="none"),
           p3 + theme(legend.position="none"),
           align = 'vh',
           labels = c("A", "B", "C"),
           hjust = -1,
           nrow = 1
           )
legend_b <- get_legend(p1 + theme(legend.position="bottom"))

# add the legend underneath the row we made earlier. Give it 10% of the height
# of one plot (via rel_heights).
p <- plot_grid( prow, legend_b, ncol = 1, rel_heights = c(1, .2))
p

此示例显示了一个绘图,其中绘制的图例与网格的左下角对齐.然而,它过去是不同的,因为图例然后绘制为与图的底部中心对齐.以下是几个月前由我的个人代码生成的示例. https://s1.postimg.org/8pf2en1zen/Untitled.png(上传工具目前不适合我)

在任一包中发生未知数量的更改之后重新运行我的旧代码会传递与左下角对齐的图例(如教程中所示,上面的第三个图):https: //s1.postimg.org/3agjw7n9gf/Untitled2.png

问题是如何调整代码以绘制与底部中心对齐的图例.

Answer 1

你可以这样设置legend_b:

legend_b <- get_legend(p1 + theme(legend.position=c(0.3,0.8),legend.direction = "horizontal"))

更好的方法:

legend_b <- get_legend(p1 + theme(legend.direction = "horizontal",legend.justification="center" ,legend.box.just = "bottom"))