ggdesplot(): position num/text labels correctly when the formula has no fill variable

NEWS.md

@@ -12,6 +12,8 @@
 
 * `ggdesplot()` named `col.regions` and `col.text` now fall back to positional matching (as the warning states) when some factor levels are unnamed, instead of leaving cells uncolored. (P.Schmidt)
 
+* `ggdesplot()` now positions `num`/`text` labels correctly when the formula has no left-hand side (no fill variable, e.g. `~ col*row | block`). Previously the labels on the outer cells were clipped at the panel border because, without a filled tile, the half-cell extent was never established. (P.Schmidt)
+
 * Switch to MIT license.
 
 * Documentation pages now created via Github Actions.

R/ggdesplot.R

@@ -488,6 +488,14 @@ ggdesplot <- function(data,
   # Note, cells with a missing value are left empty instead of being filled
   # with the ggplot2 default grey50, which is hard to tell from the lightgray
   # midpoint of RedGrayBlue. The lattice version leaves such cells empty too.
+  if(fill.type=="none")
+    # No fill variable (empty formula LHS). Draw an invisible tile grid anyway
+    # so the +-0.5 cell extent is established; otherwise num/text labels on the
+    # outer cells sit on the panel border and are clipped. The lattice path
+    # reserves this extent regardless of fill.
+    out <- out +
+    geom_tile(fill = "transparent")
+
   if(fill.type=="num")
     out <- out +
     #geom_tile(aes_string(fill = fill.string)) +

tests/testthat/test_ggdesplot_fixes.R

@@ -32,13 +32,36 @@ test_that("ggdesplot does not add a spurious colour legend without 'col'", {
 })
 
 test_that("ggdesplot named col.regions fallback colours every level", {
-  p <- suppressWarnings(
-    ggdesplot(partial, rep ~ col * row, col.regions = c(R1 = "red", R2 = "blue")))
+  # the names cover only R1/R2 of four levels: a deliberate warning fires and
+  # the code falls back to positional matching. Assert the warning (not suppress
+  # it) and then check the fallback still colours every tile (no grey NA).
+  expect_warning(
+    p <- ggdesplot(partial, rep ~ col * row, col.regions = c(R1 = "red", R2 = "blue")),
+    "positional"
+  )
   b <- ggplot2::ggplot_build(p)
-  # no tile should be left unfilled (grey NA) by the positional fallback
   expect_false(any(is.na(b$data[[1]]$fill)))
 })
 
+test_that("ggdesplot with no fill variable keeps num/text labels inside the panel", {
+  # Empty LHS: cells carry only numbers (num=), no fill. Without a tile to
+  # establish the +-0.5 cell extent, boundary labels are drawn on the panel
+  # edge and get clipped (the num= plot looked wrong). A transparent tile grid,
+  # as in the lattice path, must provide that extent.
+  blk <- expand.grid(col = 1:2, row = 1:3, block = c("B1", "B2"))
+  blk$block <- factor(blk$block)
+  blk$g     <- factor(rep(1:3, length.out = nrow(blk)))
+  p <- ggdesplot(blk, ~ col * row | block, num = g)
+  b <- ggplot2::ggplot_build(p)
+  rng <- b$layout$panel_params[[1]]$x.range
+  # the drawn range must reach half a cell beyond the outer column centres,
+  # otherwise a label at col 1 or col 2 sits on the panel border
+  expect_lte(rng[1], 0.5)
+  expect_gte(rng[2], 2.5)
+  # the extent comes from a (transparent) tile layer, not from the text alone
+  expect_true(any(vapply(p$layers, function(l) inherits(l$geom, "GeomTile"), logical(1))))
+})
+
 test_that("ggdesplot facets on every conditioning variable", {
   p <- ggdesplot(twocond, y ~ x * row | site + rep)
   b <- ggplot2::ggplot_build(p)