如何在ggplot2绘图的副标题中添加R-squared值？

当然可以直接修改代码把R-squared值添加到副标题里，你只需要先计算线性回归模型的R²，再把它格式化后放到labs()的subtitle参数里就行。

修改后的完整代码（提前计算R²，逻辑更清晰） #

library(ggplot2)

set.seed(123)

n <- 100
x <- rnorm(n, mean = 50, sd = 10)
y <- 2 + 0.5 * x + rnorm(n, mean = 0, sd = 15)

sim_data <- data.frame(x = x, y = y)

# 计算线性回归模型的R²值
r_squared <- summary(lm(y ~ x, data = sim_data))$r.squared

ggplot(sim_data, aes(x = x, y = y)) +
    geom_point(color = "steelblue", alpha = 0.7, size = 3) +
    geom_smooth(method = "lm", color = "darkred", size = 1) +
    theme_minimal() +
    labs(
        title = "Scatterplot with Regression Line and Confidence Interval",
        subtitle = paste0("R² = ", round(r_squared, 3)), # 添加带R²的副标题
        x = "X Variable",
        y = "Y Variable"
    ) +
    theme(
        plot.title = element_text(face = "bold", size = 14),
        axis.title = element_text(face = "bold"),
        plot.subtitle = element_text(face = "italic") # 可选：给副标题添加样式
    )

紧凑版（直接嵌入计算逻辑） #

如果不想单独提前计算R²，也可以把计算逻辑直接写到subtitle参数里，代码会更简洁：

ggplot(sim_data, aes(x = x, y = y)) +
    geom_point(color = "steelblue", alpha = 0.7, size = 3) +
    geom_smooth(method = "lm", color = "darkred", size = 1) +
    theme_minimal() +
    labs(
        title = "Scatterplot with Regression Line and Confidence Interval",
        subtitle = paste0("R² = ", round(summary(lm(y ~ x, data = sim_data))$r.squared, 3)),
        x = "X Variable",
        y = "Y Variable"
    ) +
    theme(
        plot.title = element_text(face = "bold", size = 14),
        axis.title = element_text(face = "bold")
    )

两种方式都能实现需求，前者逻辑更直观，后者代码更紧凑，可根据习惯选择。

内容的提问来源于stack exchange，提问作者stats_noob