How to add legend to hline and vline together?

Question

I want to add two vertical line and two horizontal line to existing ggplot with legend.

I have tried this:

library(ggplot2)

x <- c(1:70)
y <- c((1:70)^2)
df <- data.frame(x,y)

ggplot(df, aes(x = x, y = y)) +
  ylab(expression(bold("Height"))) +
  xlab(expression(bold("Width"))) +
  geom_point(size=1, col="red") +
  geom_hline(aes(yintercept=2000, linetype = "1st border of height"),col="green",size=1) +
  geom_hline(aes(yintercept=4000, linetype = "2st border of height"), col="red", size=1) +
  geom_vline(aes(xintercept=20, linetype = "1st border of width"), col="blue", size=1, linetype="dashed") +
  geom_vline(aes(xintercept=40, linetype = "2st border of width"),col="darkblue", size=1, linetype="dashed") +
  geom_smooth(lwd=1, col="blue", span = 0.8, se=F) +
  scale_linetype_manual(name = "Legend", values = c(1,2,1,1), 
                    guide = guide_legend(override.aes = list(color = c("green", "red", "blue", "darkblue")))) + 
  theme()

Can somebody help me?

Answer 1

You can try

x <- c(1:70)
y <- c((1:70)^2)
df <- data.frame(x,y)
df_lines <- data.frame(type = factor(rep(c("yintercept", "xintercept"), each = 2)), y = c(2000, 4000, 20, 40), border_of_height = as.character(1:2))

ggplot(df, aes(x = x, y = y)) +
  ylab(expression(bold("Height"))) +
  xlab(expression(bold("Width"))) +
  geom_point(size=1, col="red") +
  geom_smooth(lwd=1, col="blue", span = 0.8, se=F) +
  geom_hline(data = df_lines[1:2, ], aes(yintercept = y, color = border_of_height, linetype = type)) +
  geom_vline(data = df_lines[3:4, ], aes(xintercept = y, color = border_of_height, linetype = type), show.legend = F)