Smart x/ylim arguments

[grantmcdermott]

Fixes #616

MWE

Reference plot for comparison.

pkgload::load_all("~/Documents/Projects/tinyplot/")
#> ℹ Loading tinyplot
plt(dist ~ speed, data = cars)

1. Scalar input ensures value coverage (here: x value is binding, but the y value isn't).

plt(dist ~ speed, data = cars, xlim = 0, ylim = 100)

2. Partial NA pins one limit, let data set the other.

plt(dist ~ speed, data = cars, xlim = c(0, NA))

3. "rev(erse)" keyword

plt(dist ~ speed, data = cars, xlim = "reverse")

^{Created on 2026-06-23 with reprex v2.1.1}

[grantmcdermott]

@zeileis @vincentarelbundock Sorry to tag you (again!) but I promise that this is the final time before I submit 0.7.0. I'd like your feedback, since this is an API change (which I like, but you might feel differently).

I'm confident in the implementation, so no need to check the internal code. Just let me know whether you like the API.

[Copilot]

Pull request overview

This PR implements “smart” xlim/ylim override forms in tinyplot, adding support for scalar coverage (ensure a value is included), partial-NA limit pinning, and a "rev(erse)" keyword to reverse automatically computed axis limits (Fixes #616).

Changes:

• Extend xlim/ylim parsing to support scalar inputs, length-2 partial NA, and "rev(erse)" keyword reversal.
• Plumb new rev_x/rev_y flags through settings, limit computation, flip handling, and facet drawing (including free-scale facets).
• Add snapshot tests and documentation/NEWS updates describing the new limit behaviors.

Reviewed changes

Copilot reviewed 7 out of 13 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
R/zzz.R	Registers new rev_x/rev_y globals to satisfy R CMD check.
R/tinyplot.R	Adds docs for new xlim/ylim forms; resolves "rev(erse)" into rev_x/rev_y settings.
R/lim.R	Adds resolve_lim() and applies smart limit resolution; reverses finalized limits based on rev_x/rev_y.
R/flip.R	Ensures rev_x/rev_y are swapped when flipping axes.
R/facet.R	Threads rev_x/rev_y into facet window drawing; attempts to support reversed axes under free facets.
NEWS.md	Documents the new “smart” x/ylim override forms.
man/tinyplot.Rd	Updates rendered documentation for new xlim/ylim behaviors.
man/facet.Rd	Documents new internal rev_x/rev_y parameters for draw_facet_window().
inst/tinytest/test-lim.R	Adds snapshot tests covering scalar coverage, partial-NA pinning, and "reverse" (incl. free facets).
inst/tinytest/_tinysnapshot/lim_scalar_zero.svg	New snapshot output for scalar coverage test.
inst/tinytest/_tinysnapshot/lim_reverse.svg	New snapshot output for reverse keyword test.
inst/tinytest/_tinysnapshot/lim_reverse_free_facet.svg	New snapshot output for reverse keyword with free facets.
inst/tinytest/_tinysnapshot/lim_partial_na.svg	New snapshot output for partial-NA pinning test.

Files not reviewed (2)

• man/facet.Rd: Generated file
• man/tinyplot.Rd: Generated file

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.