June 2020
Beginner to intermediate
522 pages
9h 6m
Chinese
Content preview from R 语言经典实例（原书第 2 版）
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图形
｜
285
ggplot 允许我们对不同的 geom_ 函数进行多次调用，每个 geom_ 函数都有自己的数
据源（如果需要）。然后 ggplot 将查看我们正在绘制的所有数据，并调整范围以适应
所有数据。
绘制两个数据集的结果如图 10-38 所示。
0 10 20 30
x1
2
1
0
-
1
y1
图 10-38：一幅图中包含两条线
10.16 添加垂直线和水平线
10.16.1 问题
需要在绘图中添加垂直线或水平线，例如通过原点的轴或指向阈值的指针。
10.16.2 解决方案
ggplot 函数 geom_vline 和 geom_hline 分别生成垂直线和水平线。这些函数还可
以使用参数 color、linetype 和 size 来设置线条样式：
# using the data.frame df1 from the prior recipe
ggplot(df1) +
aes(x = x1, y = y1) +
geom_point() +
geom_vline(
xintercept = 10,
color = "red",
linetype = "dashed",
size = 1.5
286
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10
章
) +
geom_hline(yintercept = 0, color = "blue") ...
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