在ggplot的顶部和右侧添加轴刻度线？

Question

在base图形中,我们可以通过使用axis和side参数轻松地在图的不同侧面添加刻度标记:

par(tck = 0.025)
plot(1:10)
axis(side = 3, labels = FALSE)
axis(side = 4, labels = FALSE)

如何在顶部和右侧镜像x和y轴刻度ggplot2？有annotation_logticks可以做到这一点,但似乎只适用于对数标度(因为函数的名称适用).对于线性刻度,是否有类似的简单方法？

Answer 1

从ggplot2 2.2.0你可以使用sec.axis参数scale_.

dup_axis 是创建辅助轴的简写,辅助轴是主轴的复制,有效地镜像主轴.

ggplot(data = mpg, aes(x = displ, y = hwy)) + 
  geom_point() +
  scale_x_continuous(sec.axis = dup_axis()) +
  scale_y_continuous(sec.axis = dup_axis())

Answer 2

这会镜像轴刻度线（使用gtable函数），并将刻度线放入绘图面板内。

2016 年 4 月 18 日编辑 axis.ticks.margin已弃用。请改用文本边距。

编辑 19 Mrch 2015：更好地定位刻度线

library(ggplot2) # v2.1.0
library(gtable)  # v0.2.0
library(grid)

# Get a plot
p = ggplot(data.frame(x = 1:10, y = 1:10), aes(x,y)) + 
   geom_point() +
   theme_bw() +
   theme(panel.grid = element_blank(),
          axis.ticks.length=unit(-0.25, "cm"),
          axis.text.x = element_text(margin = margin(t = .5, unit = "cm")),
          axis.text.y = element_text(margin = margin(r = .5, unit = "cm")))

# Convert the plot to a grob
gt <- ggplotGrob(p)

# Get the position of the panel in the layout
panel <-c(subset(gt$layout, name=="panel", se=t:r))

## For the bottom axis
# Get the row number of the bottom axis in the layout
rn <- which(gt$layout$name == "axis-b")

# Extract the axis (tick marks only)
axis.grob <- gt$grobs[[rn]]
axisb <- axis.grob$children[[2]]  # Two children - get the second
axisb  # Note: two grobs - tick marks and text

# Get the tick marks
xaxis = axisb$grobs[[1]]  # NOTE: tick marks first
xaxis$y = xaxis$y - unit(0.25, "cm")  # Position them inside the panel

# Add a new row to gt, and insert the revised xaxis grob into the new row.
gt <- gtable_add_rows(gt, unit(0, "lines"), panel$t-1)
gt <- gtable_add_grob(gt, xaxis, l = panel$l, t = panel$t, r = panel$r, name = "ticks")

## Repeat for the left axis
# Get the row number of the left axis in the layout
panel <-c(subset(gt$layout, name=="panel", se=t:r))
rn <- which(gt$layout$name == "axis-l")

# Extract the axis (tick marks and axis text)
axis.grob <- gt$grobs[[rn]]
axisl <- axis.grob$children[[2]]  # Two children - get the second
axisl  # Note: two grobs -  text and tick marks

# Get the tick marks
yaxis = axisl$grobs[[2]] # NOTE: tick marks second
yaxis$x = yaxis$x - unit(0.25, "cm") # Position them inside the panel

# Add a new column to gt, and insert the revised yaxis grob into the new column.
gt <- gtable_add_cols(gt, unit(0, "lines"), panel$r)
gt <- gtable_add_grob(gt, yaxis, t = panel$t, l = panel$r+1, name = "ticks")

# Turn clipping off
gt$layout[gt$layout$name == "ticks", ]$clip = "off"

# Draw it
grid.draw(gt)