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ggplot2中添加直线的geoms一共有几种。今天系统总结一下。
geom_hline和geom_vline
library(ggplot2)
library(dplyr)
## Warning: package 'dplyr' was built under R version 3.6.1
##
## Attaching package: 'dplyr'
## The following objects are masked from 'package:stats':
##
## filter, lag
## The following objects are masked from 'package:base':
##
## intersect, setdiff, setequal, union
library(magrittr)
## Warning: package 'magrittr' was built under R version 3.6.1
plot <-
mtcars %>%
ggplot() +
geom_point(aes(mpg, disp, colour = gear)) +
theme_bw()
geom_hline和geom_vline分别用来添加水平线（horizontal）和垂直线（vertical）
plot +
geom_hline(yintercept = 300) +
geom_vline(xintercept = 20)
如果只是要添加单条或者多条确定的直线，则只需要设置yintercept和xintercept参数即可。当然，可以通过colour，size，linetype来设置线条的外观等。 plot +
geom_hline(yintercept = c(300, 400), colour = 'red', linetype = 2, size = 2) +
geom_vline(xintercept = c(20, 25), colour = 'blue', linetype = 3, size = 3)
同样的，他们也支持aes形式。 temp.data <- data.frame(x = c(1,2,3), y = c(100,200,300),
stringsAsFactors = FALSE)
plot +
geom_hline(aes(yintercept = y, size = y), data = temp.data)
这个时候，一些配套的参数，比如show.legend才开始起作用。 plot +
geom_vline(aes(xintercept = y, size = y), data = temp.data,
show.legend = FALSE)
geom_abline
geom_abline可以用来画有斜率的直线，比如画对角线（截距为0，斜率为1）。
plot +
geom_abline(slope = 1, intercept = 0) +
scale_x_continuous(limits = c(0,300)) +
scale_y_continuous(limits = c(0,300))
## Warning: Removed 11 rows containing missing values (geom_point).
同样的，也可以通过设置colour，size，linetype来设置线条的外观等。 当然，geom_abline也支持aes mapping方式来设置不同的直线。 temp.data <- data.frame(intercept = c(0, 0, 0),
slope = c(1, 0.5, 0.8),
stringsAsFactors = FALSE)
temp.data$slope <- factor(temp.data$slope)
library(ggnewscale)
## Warning: package 'ggnewscale' was built under R version 3.6.1
plot +
ggnewscale::new_scale_color() +
geom_abline(aes(intercept = intercept,
slope = slope,colour = slope),
data = temp.data, size = 1.5) +
scale_x_continuous(limits = c(0,300)) +
scale_y_continuous(limits = c(0,300))
## Scale for 'x' is already present. Adding another scale for 'x', which
## will replace the existing scale.
## Scale for 'y' is already present. Adding another scale for 'y', which
## will replace the existing scale.
## Warning: Removed 11 rows containing missing values (geom_point).
## Warning in Ops.factor(ranges$x[1], data$slope): '*' not meaningful for
## factors
## Warning in Ops.factor(ranges$x[2], data$slope): '*' not meaningful for
## factors
## Warning: Removed 3 rows containing missing values (geom_segment).
注意：这里用到了ggnewscale包里面的new_scale_color()函数。因为如果不使用它，会导致两个都mapping到colour的legend融合到一起，也就是后面的覆盖到了前面的。我们可以看看效果。
plot +
geom_abline(aes(intercept = intercept,
slope = slope,colour = slope),
data = temp.data, size = 1.5) +
scale_x_continuous(limits = c(0,300)) +
scale_y_continuous(limits = c(0,300))
## Warning: Removed 11 rows containing missing values (geom_point).
## Warning in Ops.factor(ranges$x[1], data$slope): '*' not meaningful for
## factors
## Warning in Ops.factor(ranges$x[2], data$slope): '*' not meaningful for
## factors
## Warning: Removed 3 rows containing missing values (geom_segment).
geom_segment
geom_segment也可以用来添加直线，但是更为灵活，也就是可以设定起始点，而不是贯穿整个图。
通过设置起始点坐标添加直线其中，arrow参数可以和arrow()配合使用，来设置箭头。 plot +
geom_segment(x = 15, xend = 30, y = 300, yend = 300,
colour = 'red', linetype = 1, size = 2,
lineend = 'round', arrow = arrow(ends = 'both')) +
geom_segment(x = 15, xend = 30, y = 200, yend = 200,
colour = 'red', linetype = 1, size = 2, lineend = 'butt') +
geom_segment(x = 15, xend = 30, y = 100, yend = 100,
colour = 'red', linetype = 1, size = 2, lineend = 'square')
aes
temp.data <- data.frame(x = c(15, 15, 15),
xend = c(30, 30, 30),
y = c(300, 200, 100),
yend = c(300, 200, 100),
stringsAsFactors = FALSE)
plot +
geom_segment(aes(x = x, xend = xend, y = y, yend = yend),
data = temp.data)
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