ggplot2 分面绘图
主要介绍ggplot2里Facetting使用要点。
Facetting用于将图以面板矩阵的形式分成多个子图进行绘制，主要通过以下函数实现[1]。
facet_grid()facet_wrap()
一些常规设置参考此文[2]，下面是我使用时调整的一些内容。
面板标签模块设置
Label替换
这部分内容在facet_grid/warp()里调整
# 构造替换字典
# 新label
supp.labs <- c("Orange Juice", "Vitamin C")
# 原label
names(supp.labs) <- c("OJ", "VC")
# 在labeller中进行替换
p + facet_grid(
. ~ supp,
labeller = labeller(supp = supp.labs)
)字体及背景色
这部分在theme()里调整，与分面相关的属性以strip开头。
theme(
# 文字样式调整
strip.text.x = element_text(
size = 12, color = "red", face = "bold.italic"),
# 标签背景色调整，fill表示填充色，color表示边框颜色
strip.background = element_rect(
color="black", fill="#FC4E07", size=1.5, linetype="solid"))为不同子图增加标注
从facet_实现考虑，分页字段可以看作子图索引（二维），因此通过创建包含分页字段的标注子数据集，在绘图时就可以在指定子图上加入特定标注[3]。
# 载入包
library(ggplot2)
library(Rmisc)
# 载入数据
butter <- read.table("xxx", header = TRUE)
# summary数据
buttersum <- summarySE(data = butter, measurevar = "winglen",
groupvars = c("spp", "sex", "region"))
# 为标注创建数据集，包含region这个分面字段，这一步是关键
anno <- data.frame(x1 = c(1.75, 0.75), x2 = c(2.25, 1.25),
y1 = c(36, 36), y2 = c(37, 37),
xstar = c(2, 1), ystar = c(38, 38),
lab = c("***", "**"),
region = c("North", "South"))标注形态如下
# 绘制图像，选择region作为分面
ggplot(data = buttersum, aes(x = spp, y = winglen)) +
geom_point(aes(shape = sex), position = position_dodge(width = 1), size = 2)+
scale_shape_manual(values = c(1, 19), labels = c("Female", "Male") )+
geom_errorbar(aes(group = sex, ymin = winglen - se, ymax = winglen + se),
width = .2, position = position_dodge(width = 1)) +
geom_text(data = anno, aes(x = xstar, y = ystar, label = lab)) +
geom_segment(data = anno, aes(x = x1, xend = x1,
y = y1, yend = y2),
colour = "black") +
geom_segment(data = anno, aes(x = x2, xend = x2,
y = y1, yend = y2),
colour = "black") +
geom_segment(data = anno, aes(x = x1, xend = x2,
y = y2, yend = y2),
colour = "black")+
facet_grid(. ~ region)
