Force the origin to start at 0

Question

How can I set the origin / interception of the y-axis and x-axis in ggplot2?

The line of the x-axis should be exactly at y=Z.

With Z=0 or another given value.

Solution 1

xlim and ylim don't cut it here. You need to use expand_limits, scale_x_continuous, and scale_y_continuous. Try:

df <- data.frame(x = 1:5, y = 1:5)
p <- ggplot(df, aes(x, y)) + geom_point()
p <- p + expand_limits(x = 0, y = 0)
p # not what you are looking for

p + scale_x_continuous(expand = c(0, 0)) + scale_y_continuous(expand = c(0, 0))

You may need to adjust things a little to make sure points are not getting cut off (see, for example, the point at x = 5 and y = 5.

Solution 2

Simply add these to your ggplot:

+ scale_x_continuous(expand = c(0, 0), limits = c(0, NA)) + 
  scale_y_continuous(expand = c(0, 0), limits = c(0, NA))

Example

df <- data.frame(x = 1:5, y = 1:5)
p <- ggplot(df, aes(x, y)) + geom_point()
p <- p + expand_limits(x = 0, y = 0)
p # not what you are looking for


p + scale_x_continuous(expand = c(0, 0), limits = c(0,NA)) + 
  scale_y_continuous(expand = c(0, 0), limits = c(0, NA))

Lastly, take great care not to unintentionally exclude data off your chart. For example, a position = 'dodge' could cause a bar to get left off the chart entirely (e.g. if its value is zero and you start the axis at zero), so you may not see it and may not even know it's there. I recommend plotting data in full first, inspect, then use the above tip to improve the plot's aesthetics.

Solution 3

In the latest version of ggplot2, this can be more easy.

p <- ggplot(mtcars, aes(wt, mpg))
p + geom_point()
p+ geom_point() + scale_x_continuous(expand = expansion(mult = c(0, 0))) + scale_y_continuous(expand = expansion(mult = c(0, 0)))

See ?expansion() for more details.

Comments

[JelenaČuklina]

I also needed to specify limits: scale_x_continuous(expand = c(0, 0), limits = c(0,5)), somehow without it it didn't work

[Michael Roswell]

I think one more piece can be helpful, which is using something like expand=expand_scale(mult=c(0,0.1)) so you still get the padding at the upper ends: stackoverflow.com/a/59056123/8400969

[Bolle]

is it also possible to build this into a new ggplot theme?

[stevec]

@Bolle I’m not sure, but interested to find out as well, you could ask as a separate question and link to here

[stevec]

Link here for future reference

[Melkor.cz]

This only changes padding around data points, but does not help set axes origin to zero or other desired value.