Adding horizontal lines in the plot of a step function

[amgarcia]

Hello!
I attach graphic, image.jpg, in which I want to draw the line y=0 for x<3 and the line y=1 for x>=8, i.e. the result would be image2.jpg.

These are the instructions for image.jpg.

df <- data.frame(x=Asignaturas, y=solF)
df$xend <- c(df$x[2:nrow(df)],NA)
df$yend <- df$y
p <- (ggplot(df, aes(x=x, y=y, xend=xend, yend=yend)) +
geom_vline(aes(xintercept=x), linetype=2,color="grey") +
geom_point() + # Solid points to left
geom_point(aes(x=xend, y=y), shape=1) + # Open points to right
geom_segment()# Horizontal line
+geom_text(aes(label = paste0(solF,''),vjust = -0.5), color = "black")+ylab("Función de distribucción")+ xlab("Asignaturas"))

p

Does anyone know how to do it?

Thanks

[pieterjanvc]

Hi,

You can do this by adding two more segments that represent the top and bottom horizontal line, make sure they start / end outside the area you want to crop, them crop the plot by limiting the x-axis

library(ggplot2)

#Data points
myData = data.frame(
  x = 1:5,
  xend = 2:6,
  y = 1:5,
  yend = 1:5
)

#Horizontal lines
ends = data.frame(
  x = c(0,6),
  xend = c(1,7),
  y = c(0,6),
  yend = c(0,6)
)

#Plot
ggplot(myData) + 
  geom_segment(aes(x=x, y=y, xend=xend, yend=yend)) +
  geom_segment(data = ends, aes(x=x, y=y, xend=xend, yend=yend), color = "red") +
  coord_cartesian(xlim=c(0.8,6.2))

^{Created on 2021-11-22 by the reprex package (v2.0.1)}

Of note: you have to use the coord_cartesian() function to set the limit, because if you would just use the xlim() function it would remove the red lines since they are not fully displayed

[amgarcia]

Thank you very much!

For any data set, it also works:

extraLines <- data.frame(x = c(-Inf, max(df$x)), xend = c(min(df$x), Inf), y = c(0, max(df$y)), yend = c(0, max(df$y)))

p +
  geom_segment(data = extraLines, aes(x = x, xend = xend, y = y, yend = yend), colour = "red") +
  geom_point(data = filter(extraLines, x > 0), aes(x = x, y=y), colour = "red") + 
  geom_point(data = filter(extraLines, x < max(df$x)), aes(x=xend, y=y), shape = 1, colour = "red")