R ggplot set ymax but not ymin without cutting data

I want to set a ggplot's max y value while keeping the default min y but I need to use coord_cartesian as I want to zoom in, not exclude any data from calculations.

I'm surprised that I couldn't find the answer to this. There are many questions answering how to expand limits to a certain value or set only one limit using scale_._.. but I can't find any using coord_cartesian to set only one limit

For example; using the example plot from ?coord_cartesian:

library(ggplot2)
p <- ggplot(mtcars, aes(disp, wt)) +
  geom_point() +
  geom_smooth()

I want the equivalent of

p + coord_cartesian(ylim = c(1.5, 4))

without having to set 1.5 as the min.

If I could use scale_y_continuous I could use

p + scale_y_continuous(limits = c(NA, 4))

but this limits all data contributing to my smooth to values less than 4 which I don't want, and the equivalent p + coord_cartesian(ylim = c(NA, 4)) returns an error.

Is there an easy replacement?

I could also come up with a calculation based on the data of the min of the plot, but this could become complicated if I am faceting the plot or similar.

Solution

This issue was fixed in ggplot2 3.3.0 on 5-Mar-2020.

Now coord_cartesian(ylim = c(NA, 4)) runs without errors.

Example

library(ggplot2)
p <- ggplot(mtcars, aes(disp, wt)) +
  geom_point() +
  geom_smooth() + 
  coord_cartesian(ylim = c(NA, 4))

Below is the description of the feature in the NEWS file (bullet 2 under 'New features').

All coord_*() functions with xlim and ylim arguments now accept vectors with NA as a placeholder for the minimum or maximum value (e.g., ylim = c(0, NA) would zoom the y-axis from 0 to the maximum value observed in the data). This mimics the behaviour of the limits argument in continuous scale functions (@paleolimbot, #2907).