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ggplot2中添加直線(xiàn)的geoms一共有幾種。今天系統(tǒng)總結(jié)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分別用來(lái)添加水平線(xiàn)（horizontal）和垂直線(xiàn)（vertical）
plot +
geom_hline(yintercept = 300) +
geom_vline(xintercept = 20)
如果只是要添加單條或者多條確定的直線(xiàn)，則只需要設(shè)置yintercept和xintercept參數(shù)即可。當(dāng)然，可以通過(guò)colour，size，linetype來(lái)設(shè)置線(xiàn)條的外觀等。 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)
同樣的，他們也支持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)
這個(gè)時(shí)候，一些配套的參數(shù)，比如show.legend才開(kāi)始起作用。 plot +
geom_vline(aes(xintercept = y, size = y), data = temp.data,
show.legend = FALSE)
geom_abline
geom_abline可以用來(lái)畫(huà)有斜率的直線(xiàn)，比如畫(huà)對(duì)角線(xiàn)（截距為0，斜率為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).
同樣的，也可以通過(guò)設(shè)置colour，size，linetype來(lái)設(shè)置線(xiàn)條的外觀等。 當(dāng)然，geom_abline也支持aes mapping方式來(lái)設(shè)置不同的直線(xiàn)。 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：這里用到了ggnewscale包里面的new_scale_color()函數(shù)。因?yàn)槿绻皇褂盟?，?huì)導(dǎo)致兩個(gè)都mapping到colour的legend融合到一起，也就是后面的覆蓋到了前面的。我們可以看看效果。
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也可以用來(lái)添加直線(xiàn)，但是更為靈活，也就是可以設(shè)定起始點(diǎn)，而不是貫穿整個(gè)圖。
通過(guò)設(shè)置起始點(diǎn)坐標(biāo)添加直線(xiàn)其中，arrow參數(shù)可以和arrow()配合使用，來(lái)設(shè)置箭頭。 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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