ggplot2：在每个构面上添加回归线方程时，x轴存在问题

Question

基于此处的示例 Adding Regression Line Equation and R2 on graph，我正在努力在每个方面都包括模型的回归线方程。但是，我不知道为什么要更改x轴的限制。

library(ggplot2)
library(reshape2)

df <- data.frame(year = seq(1979,2010), M02 = runif(32,-4,6), 
M06 = runif(32, -2.4, 5.1), M07 = runif(32, -2, 7.1))
df <- melt(df, id = c("year"))


ggplot(data = df, mapping = aes(x = year, y = value)) +
geom_point() +
scale_x_continuous() + 
stat_smooth_func(geom = 'text', method = 'lm', hjust = 0, parse = T) +
geom_smooth(method = 'lm', se = T) +
facet_wrap(~ variable) # as you can see, the scale_x_axis goes back to 1800

如果我在x上加上了限制，

scale_x_continuous(limits = c(1979,2010)) 

它不再显示回归系数。我在这里做什么错了？

stat_smooth_func在此处可用： https://gist.github.com/kdauria/524eade46135f6348140

Answer 1

您可以使用ggpmisc软件包中的stat_poly_eq功能。

library(reshape2)
library(ggplot2)
library(ggpmisc)
#> For news about 'ggpmisc', please, see https://www.r4photobiology.info/
#> For on-line documentation see https://docs.r4photobiology.info/ggpmisc/

df <- data.frame(year = seq(1979,2010), M02 = runif(32,-4,6), 
                 M06 = runif(32, -2.4, 5.1), M07 = runif(32, -2, 7.1))
df <- melt(df, id = c("year"))

formula1 <- y ~ x

ggplot(data = df, mapping = aes(x = year, y = value)) +
  geom_point() +
  scale_x_continuous() + 
  geom_smooth(method = 'lm', se = TRUE) +
  stat_poly_eq(aes(label = paste(..eq.label.., ..rr.label.., sep = "~~~~")), 
               label.x = "left", label.y = "top",
               formula = formula1, parse = TRUE, size = 3) +
  facet_wrap(~ variable) 

ggplot(data = df, mapping = aes(x = year, y = value)) +
  geom_point() +
  scale_x_continuous() + 
  geom_smooth(method = 'lm', se = TRUE) +
  stat_poly_eq(aes(label = paste(..eq.label.., sep = "~~~")), 
               label.x = "left", label.y = 0.15,
               eq.with.lhs = "italic(hat(y))~`=`~",
               eq.x.rhs = "~italic(x)",
               formula = formula1, parse = TRUE, size = 4) +
  stat_poly_eq(aes(label = paste(..rr.label.., sep = "~~~")), 
               label.x = "left", label.y = "bottom",
               formula = formula1, parse = TRUE, size = 4) +
  facet_wrap(~ variable) 

^{由reprex package（v0.2.1.9000）于2019-01-10创建}

Answer 2

可能有人会建议一个更好的解决方案，但是作为替代，您可以更改stat_smooth_func，并可以像这样最后一行

data.frame(x=1979, y=ypos, label=func_string)

代替

data.frame(x=xpos, y=ypos, label=func_string)

所以，情节如下图