Feature request: `position_step()`

[teunbrand]

We now have geom_step(). The 'step' adjustment to the line could in theory work with other geometries as well, notably geom_area() or even geom_ribbon(). The proposal here is to make a position_step() and deprecate GeomStep in favour of GeomLine + PositionStep.

[teunbrand]

I've come to realise that we could even generalise on the step adjustment by allowing arbitrary connections between points.

[smouksassi]

one consideration/complication for ribbons is how to close the last part of ribbon especially if it is a CI around say a geom_stop of a kaplan meier curves:
https://adibender.github.io/pammtools/reference/geom_stepribbon.html
https://github.com/smouksassi/ggquickeda/blob/main/R/ggkm.R#L750

[teunbrand]

Thanks for the links @smouksassi! I have the feeling like I'm missing some subtlety here. Do KMCs have some special rules about how the steps should be drawn?

I think {ggsurvfit}, which I trust on their KMCs, uses direction = "hv" by default (https://github.com/pharmaverse/ggsurvfit/blob/main/R/stat_stepribbon.R).

[smouksassi]

harrelfe/rms#70
I will have to prepare something specific to KM, before deciding geom_kmbands I had to review what is available and what was different between the various solutions. from what I remember it is mainly the last point and how to close it that might be different between "methods"

[teunbrand]

If we now already have 4 examples of packages had to reimplement the steps, then I suppose that indicates some need to support this at the base ggplot2 level beyond geom_step()😅