Could ggplot support positioning the axis within the panel (e.g. in guide_axis)?

[davidhodge931]

Apologies if this has already been asked.

Sometimes it might be wanted to place an axis within a panel (e.g. at zero).

I was wondering if it was possible for dup_axis to provide this functionality?

So something like this for a y axis intercepting the x at 0..

p +
  scale_y_continuous(
    sec.axis = dup_axis(
      xintercept = 0,
    )
  )

[teunbrand]

The dup_axis() is more of a specifier for a secondary axis and its parameters, rather than an axis placement specifier. I don't think it'd be the most natural fit for this function to take on such functionality. I've made something similar to what you describe in https://teunbrand.github.io/ggh4x/reference/coord_axes_inside.html, but implemented as a coord rather than secondary axis.

[davidhodge931]

That's super nice!

[davidhodge931]

Maybe conceptually it should ideally go in a guide? I.e. guide_axis(xintercept = 0)

[teunbrand]

Interesting; it is definitely a more intuitive place than in coords. It would not be easy for a guide extension to do it, so I would think the right place for it is in ggplot2 itself. I'm re-opening this because we should at least explore a bit how feasible this is.