How to stop ggplot line plot adding fill

Question

I am producing a ggplot which looks at a curve in a dataset. When I build the plot, ggplot is automatically adding fill to data which is on the negative side of the x axis. Script and plot shown below.

ggplot(df, aes(x = Var1, y = Var2)) +
 geom_line() + 
 geom_vline(xintercept = 0) +
 geom_hline(yintercept = Var2[1])

Using base R, I am able to get the plot shown below which is how it should look.

plot(x = df$Var1, y = df$Var2, type = "l",
 xlab = "Var1", ylab = "Var2")
abline(v = 0) 
abline(h = df$Var2[1])

If anyone could help identify why I might be getting the automatic fill and how I could make it stop, I would be very appreciative. I would like to make this work in ggplot so I can later animate the line as it is a time series that can be used to compare between other datasets from the same source.

Can add data if necessary. Data set is 1561 obs long however. Thanks in advance.

Martin Gal Martin Gal · Accepted Answer · 2020-04-19T21:40:11

I guess you should try

ggplot(df, aes(x = Var1, y = Var2)) +
  geom_path() + 
  geom_vline(xintercept = 0) +
  geom_hline(yintercept = Var2[1])

instead. The geom_line()-function connects the points in order of the variable on the x-axis.

Take a look at this example

dt <-  data.frame(
  x = c(seq(-pi/2,3*pi,0.001),seq(-pi/2,3*pi,0.001)),
  y = c(sin(seq(-pi/2,3*pi,0.001)), cos(seq(-pi/2,3*pi,0.001)))
  )

ggplot(dt, aes(x,y)) + geom_line()

The two points with x-coordinate -pi/2 will be connected first, creating a vertical black line. Next x = -pi/2 + 0.001 will be processed and so on. The x values will be processed in order.

Therefore you should use geom_path() to get the desired result

dt <-  data.frame(
  x = c(seq(-pi/2,3*pi,0.001),seq(-pi/2,3*pi,0.001)),
  y = c(sin(seq(-pi/2,3*pi,0.001)), cos(seq(-pi/2,3*pi,0.001)))
 )

ggplot(dt, aes(x,y)) + geom_path()

How to stop ggplot line plot adding fill

1 Answers