tissot 0.2.0

Major refactor — modernized engine, new API, and rich plotting.

Breaking changes

• Projection engine switched from reproj to gdalraster::transform_xy(). All projection work is now a single batched GDAL call.

• API renamed: proj.in/proj.out → source/target, following reproj conventions. target is the second positional argument (required); source defaults to "EPSG:4326".

• tissot() input is now any “xy-ish” object (matrix, data.frame, list, length-2 vector) via the internal as_xy() helper. The old lambda/phi positional arguments are replaced by x.

• tissot() returns a tissot_tbl (subclassed tibble) with source and target stored as attributes. Column names changed to: x, y, dx_dlam, dy_dlam, dx_dphi, dy_dphi, scale_h, scale_k, scale_omega, scale_a, scale_b, scale_area, angle_deformation, convergence.

• indicatrix() returns an indicatrix_list (replaces indicatrixes class). Accepts tissot_tbl or raw coordinates + explicit target.

• Removed: indicatrix0(), tissot0(), .prj(), and the internal numericDeriv path. The Jacobian is now computed directly via finite differences.

New features

• plot.indicatrix() and plot.indicatrix_list() with:

  • Reference unit circle overlay (show.circle)
  • Lambda/phi direction axes (show.axes)
  • show.circle and show.axes accept TRUE, FALSE, or a named list of graphical parameters for full customization
  • Colour-coded fill via fill.by (e.g. "scale_area", "angle_deformation")

• print() and summary() methods for tissot_tbl.

• print(), length(), and [ methods for indicatrix_list.

• tissot_map() and tissot_abline() accept explicit target argument.

• as_xy() internal helper coerces diverse coordinate inputs.

• resolve_gpar() internal helper for the logical-or-list graphical parameter pattern.

Internal

• Fully vectorized Jacobian computation — no per-point loop.
• Computation uses 3N batched transform_xy() call.
• Test suite added (testthat).