使用 R 中的 Lines() 函数在绘图中添加一条线
本文将介绍如何使用 R 中的 lines() 函数在绘图中添加一条线。
在 R 中使用 lines() 函数的绘图中添加一条线
lines() 函数是 R graphics 包的一部分，用于向绘图添加线条。首先，应该调用 plot 函数来构造一个图，其中有一个由前两个参数指定的变量映射。请注意，表示 y 轴坐标的第二个参数是可选的。绘制绘图后，我们可以调用 lines() 函数并根据需要传递坐标向量以将线条添加到绘图中。plot 函数不需要为 lines() 函数绘制折线图。
library(stats)
library(babynames)
library(dplyr)
plot(cars$speed, cars$dist, type = "l", col = "red",
main = "Title of the Plot",
xlab = "Speed (mph)",
ylab = "Stopping Distance (Feet)")
lines(cars$speed, cars$dist/4 , col = "green")
legend("topleft", c("line 1", "line 2"),
lty = c(1,1),
col = c("red", "green"))
在 R 中使用 points 的绘图中添加点
与 lines() 函数类似，graphics 包提供了 points() 函数来在图中绘制点。以下示例演示了在同一绘图上进行两条线和点映射的场景。但是请注意，原始折线图是使用 plot 函数绘制的。
library(stats)
library(babynames)
library(dplyr)
plot(cars$speed, cars$dist, type = "l", col = "red",
main = "Title of the Plot",
xlab = "Speed (mph)",
ylab = "Stopping Distance (Feet)")
points(cars$speed, cars$dist, col = "blue" )
lines(cars$speed, cars$dist/4 , col = "green")
points(cars$speed, cars$dist/4 , col = "black")
legend("topleft", c("line 1", "line 2"),
lty = c(1,1),
col = c("red", "green"))
plot 和 lines 函数调用顺序影响绘图的比例
有时，使用第一个函数调用映射的数据的比例不足以进行后续映射。下一个代码片段显示其中一条线几乎超出了图中的边界。
library(stats)
library(babynames)
library(dplyr)
dat <- babynames %>%
filter(name %in% c("Alice")) %>% filter(sex=="F")
dat2 <- babynames %>%
filter(name %in% c("Mary")) %>% filter(sex=="F")
plot(dat$year, dat$n, type = "l", col = "blue",
main = "Women born with different names",
xlab = "Year",
ylab = "Number of babies born")
lines(dat2$year, dat2$n, col = "red")
请注意，可以通过手动重新排序行来解决上一个问题，如下例所示。但是，更复杂的脚本可能需要构造条件语句并动态检查 y 轴数据的最大值。
library(stats)
library(babynames)
library(dplyr)
dat <- babynames %>%
filter(name %in% c("Alice")) %>% filter(sex=="F")
dat2 <- babynames %>%
filter(name %in% c("Mary")) %>% filter(sex=="F")
dat3 <- babynames %>%
filter(name %in% c("Mae")) %>% filter(sex=="F")
plot(dat2$year, dat2$n, type = "l", col = "blue",
main = "Women born with different names",
xlab = "Year",
ylab = "Number of babies born")
lines(dat$year, dat$n, col = "red")
lines(dat3$year, dat3$n, col = "orange")
legend("topright", c("Mary", "Alice", "Mae"),
lty = c(1,1,1),
col = c("blue", "red", "orange"))
Founder of DelftStack.com. Jinku has worked in the robotics and automotive industries for over 8 years. He sharpened his coding skills when he needed to do the automatic testing, data collection from remote servers and report creation from the endurance test. He is from an electrical/electronics engineering background but has expanded his interest to embedded electronics, embedded programming and front-/back-end programming.
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