很多中文期刊，对投稿的图形，要求刻度线指向图形内部。ggplot2 怎么做到刻度线向内？其实很简单。

1 加载包

library(ggplot2)
library(svglite)

2 设置轴刻度向内

ggplot() +
  geom_text(
    aes(
      x = 1,
      y = 1,
      label = "Axes ticks inside!"
    ),
    size = 4
  ) +
  theme_classic(base_size = 14) +
  theme(
    # 设置刻度线的长度为负数即可
    axis.ticks.length = unit(-4, "pt")
  )

3 更复杂的案例

轴名称的单位上下标的设置，参考此公众号之前的推送文章。

• 在公众号聊天对话框发送 上下标，或在主页搜索 上下标 即可找到。

FONT <- "serif" # Times New Roman
SIZE <- 12

figure1 <- ggplot(
    data = mpg,
    aes(x = drv, y = hwy)
  ) +
  stat_summary(
    geom = "col",
    fun = mean,
    color = "black",
    fill = NA
  ) +
   stat_summary(
    geom = "errorbar",
    fun.data = mean_se,
    width = 0.2
  ) +
  scale_y_continuous(
    expand = expansion(mult = c(0, 0))
  ) +
  labs(
    x = "X 轴名称\nYour X title", # \n 表示换行
    y = "Y 轴名称\nYour Y title"
  ) +
  coord_cartesian(
    ylim = c(0, 30),
    clip = "off"
  ) +
  theme_classic(
    base_size = SIZE,
    base_family = FONT,
    base_line_size = 0.4
    ) +
  theme(
    axis.title = element_text(size = SIZE),
    axis.text = element_text(size = SIZE, color = "black"),
    axis.ticks = element_line(color = "black", lineend = "square"),
    axis.ticks.length = unit(-4, "pt")
  )

# PNG
ggsave(
  "figure-1.png",
  figure1,
  width = 4,
  height = 4,
  dpi = 600
)

# TIFF
# 体积很大，动不动几十兆，其实不推荐
ggsave(
  "figure-1.tiff",
  figure1,
  width = 4,
  height = 4,
  dpi = 600
)

# PDF
ggsave(
  "figure-1.pdf",
  figure1,
  width = 4,
  height = 4,
  device = cairo_pdf
)

# SVG
ggsave(
  "figure-1.svg",
  figure1,
  width = 4,
  height = 4
)