R abline() 函数 - 添加参考线
R 语言实例R abline() 函数用于在现有图形上添加直线参考线。
它可以绘制水平线、垂直线或斜线，常用于标注均值、阈值或趋势线。
abline() 函数语法格式如下：
abline(a = NULL, b = NULL, h = NULL, v = NULL,
col = "black", lty = 1, lwd = 1)
参数说明：
a, b 直线的截距和斜率，即 y = a + b*x。
h 水平线的 y 值。
v 垂直线的 x 值。
lty 线型：1=实线、2=虚线、3=点线。
lwd 线宽。
实例
# 散点图
x <- 1:20
y <- x * 3 + rnorm(20, 0, 5)
plot(x, y, main = "数据与趋势线",
xlab = "X", ylab = "Y",
col = "blue", pch = 16)
# 添加回归趋势线
abline(lm(y ~ x), col = "red", lwd = 2)
# 添加水平参照线（y 的均值）
abline(h = mean(y), col = "green", lty = 2, lwd = 2)
# 添加垂直参照线
abline(v = 10, col = "purple", lty = 3, lwd = 2)
# 图例
legend("topleft",
legend = c("回归线", "均值", "x=10"),
col = c("red", "green", "purple"),
lty = c(1, 2, 3), lwd = 2)
x <- 1:20
y <- x * 3 + rnorm(20, 0, 5)
plot(x, y, main = "数据与趋势线",
xlab = "X", ylab = "Y",
col = "blue", pch = 16)
# 添加回归趋势线
abline(lm(y ~ x), col = "red", lwd = 2)
# 添加水平参照线（y 的均值）
abline(h = mean(y), col = "green", lty = 2, lwd = 2)
# 添加垂直参照线
abline(v = 10, col = "purple", lty = 3, lwd = 2)
# 图例
legend("topleft",
legend = c("回归线", "均值", "x=10"),
col = c("red", "green", "purple"),
lty = c(1, 2, 3), lwd = 2)
执行以上代码会显示包含回归线、均值线和垂直参照线的散点图。