如何更改 R 中最佳拟合线的外观

Question

我正在尝试添加多项式最佳拟合线，但由于某种原因，它似乎在绘图上来回绘制。 我想知道我应该怎么做才能修好这条线

yhat_pol = lm(age~poly(height,2), data = Loblolly)
yhat_lin = lm(age~height, data = Loblolly)

plot(x=Loblolly$height, y=Loblolly$age, pch=16, xlab = "Height (ft)", ylab = "Age (yr)", main = "Height vs Age of Loblloy Pine Trees")
lines(Loblolly$height, predict(yhat_pol), type="l", col="green", lwd=2)
lines(Loblolly$height, predict(yhat_lin), type="l", col="red", lwd=2)
lines(sort(Loblolly$height), fitted(yhat_lin)[order(Loblolly$height)])
legend("topleft", 
        legend = c("linear","polynomial"), 
        col = c("red","green"),
        lty = 1, lwd=3) 

	高度	年龄	种子
1	4.51	3	301
15	10.89	5	301
29	28.72	10	301
43	41.74	15	301
57	52.70	20	301
71	60.92	25	301
2	4.55	3	303
16	10.92	5	303
30	29.07	10	303
44	42.83	15	303

Answer 1

你几乎拥有它。

lines(sort(Loblolly$height), predict(yhat_pol)[order(Loblolly$height)], type="l", col="green", lwd=2)

如果您使用 ggplot2，我认为数据的顺序不会导致这些问题。

Answer 2

你没有要求它，但这是 - 正如布赖恩蒙哥马利所指出的 - 一个使用ggplot2的解决方案：

library(dplyr)
library(tidyr)
library(ggplot2)


Loblolly %>%
  mutate(age_pred_pol = predict(yhat_pol),
         age_pred_lin = predict(yhat_lin)) %>% 
  ggplot(aes(x = height, y = age)) +
  geom_point() +
  geom_line(aes(y = age_pred_pol, color = "Polynomial Best Fit")) +
  geom_line(aes(y = age_pred_lin, color = "Linear Best Fit")) +
  labs(x = "Height (ft)", y = "Age (yr)", title = "Height vs Age of Loblloy Pine Trees") +
  scale_colour_manual(name = "Prediction",
                      breaks = c("Polynomial Best Fit", "Linear Best Fit"),
                      values = c("red", "green")) +
  theme_bw()

这返回