如何修改R代码实现象限散点图的整体样本拟合线需求？

需求1：保留象限拟合线 + 添加整体拟合线 #

原代码中stat_smooth因继承了aes(color = quadrant)，会按象限分组生成拟合线。要添加整体样本的拟合线，只需额外新增一个stat_smooth，并重置其分组和颜色参数，强制基于全量数据拟合：

# 创建带象限颜色编码的散点图（含象限拟合线+整体拟合线）
ggplot(iris2, aes(x = Petal.Length, y = Petal.Width, color = quadrant)) +
    geom_vline(xintercept = x_mid) +
    geom_hline(yintercept = y_mid) +
    geom_point() +
    # 根据汇总表iris_labels添加标签
    geom_label(data = iris_labels,
               aes(label = paste0("n = ", n),
                   x = x, y = y, color = NULL,
                   hjust = hjust, vjust = vjust),
               fill = NA, label.size = 0,
               show.legend = FALSE) +
    labs(title = "Quadrant Plot of Iris Data",
         x = "Petal Length",
         y = "Petal Width") +
    # 保留原象限拟合线
    stat_smooth(method = lm, formula = y ~ x) +
    # 添加整体样本拟合线（用黑色虚线区分）
    stat_smooth(aes(color = NULL, group = 1), 
                method = lm, formula = y ~ x,
                color = "black", linetype = "dashed")

解释：新增的stat_smooth通过aes(color = NULL, group = 1)取消了按象限的分组，强制基于全部数据拟合；用color = "black"和linetype = "dashed"可以和象限拟合线明显区分。

需求2：仅保留整体样本拟合线（移除象限拟合线） #

只需将原有的按象限分组的stat_smooth替换为基于全量数据的拟合，重置color和group参数即可：

# 创建带象限颜色编码的散点图（仅含整体拟合线）
ggplot(iris2, aes(x = Petal.Length, y = Petal.Width, color = quadrant)) +
    geom_vline(xintercept = x_mid) +
    geom_hline(yintercept = y_mid) +
    geom_point() +
    # 根据汇总表iris_labels添加标签
    geom_label(data = iris_labels,
               aes(label = paste0("n = ", n),
                   x = x, y = y, color = NULL,
                   hjust = hjust, vjust = vjust),
               fill = NA, label.size = 0,
               show.legend = FALSE) +
    labs(title = "Quadrant Plot of Iris Data",
         x = "Petal Length",
         y = "Petal Width") +
    # 仅添加整体样本拟合线
    stat_smooth(aes(color = NULL, group = 1), 
                method = lm, formula = y ~ x)

解释：这里的stat_smooth通过aes(color = NULL, group = 1)取消了原有的按quadrant分组的逻辑，只会生成一条基于所有样本的拟合线，同时保留了原图表的象限颜色编码等样式。

内容的提问来源于stack exchange，提问作者newfinder