Jittered layering + offsets

NEWS.md

@@ -23,10 +23,13 @@ where the formatting is also better._
 
 ### Bug fixes
 
-- Jittered plots now support Date/POSIXt axes. Thanks to @wachtermh for the bug
-  report and @vincentarelbundock for the code contribution. (#327)
-- `tinyplot_add(type = "jitter")` no longer errors when layered on top of
-  boxplot, violin, or similar categorical plot types. (#560 @grantmcdermott)
+- Several improvements/fixes to jittered plots and layering:
+  - Jittered plots now support Date/POSIXt axes. Thanks to @wachtermh for the
+     bug report and @vincentarelbundock for the code contribution. (#327)
+  - `tinyplot_add(type = "jitter")` no longer errors when layered on top of
+    boxplot, violin, or similar categorical plot types. (#560 @grantmcdermott)
+  - Jitter layers added via `tinyplot_add()` now align correctly with grouped
+    (offset) boxplot, violin, and ridge base layers. (#493 @grantmcdermott)
 
 ### Internals
 

R/tinyplot.R

@@ -795,10 +795,13 @@ tinyplot.default = function(
     ribbon.alpha  = sanitize_ribbon_alpha(NULL),
 
     # misc
-    flip          = flip,
-    dodge         = NULL,
+    add           = add,
     by            = by,
+    dodge         = NULL,
     dots          = dots,
+    flip          = flip,
+    group_offsets = NULL,
+    offsets_axis  = NULL,
     type_info     = list() # pass type-specific info from type_data to type_draw
   )
 
@@ -873,6 +876,8 @@ tinyplot.default = function(
   # ensure axis aligment of any added layers
   if (!add) {
     assign("xlabs_orig", settings[["xlabs"]], envir = get(".tinyplot_env", envir = parent.env(environment())))
+    assign(".group_offsets", settings[["group_offsets"]], envir = get(".tinyplot_env", envir = parent.env(environment())))
+    assign(".offsets_axis", settings[["offsets_axis"]], envir = get(".tinyplot_env", envir = parent.env(environment())))
   } else {
     align_layer(settings)
   }

R/type_boxplot.R

@@ -43,7 +43,7 @@ type_boxplot = function(
       boxwex = boxwex,
       staplewex = staplewex,
       outwex = outwex),
-    data = data_boxplot(),
+    data = data_boxplot(boxwex = boxwex),
     name = "boxplot"
   )
   class(out) = "tinyplot_type"
@@ -60,13 +60,9 @@ draw_boxplot = function(range, width, varwidth, notch, outline, boxwex, staplewe
 
         # Handle multiple groups
         if (ngrps > 1 && isFALSE(x_by) && isFALSE(facet_by)) {
-            boxwex_orig = boxwex
+            group_offsets = get_environment_variable(".group_offsets")
             boxwex = boxwex / ngrps - 0.01
-            at_ix = at_ix + seq(
-              -((boxwex_orig - boxwex) / 2),
-              ((boxwex_orig - boxwex) / 2),
-              length.out = ngrps
-            )[iby]
+            at_ix = at_ix + group_offsets[iby]
         }
 
         boxplot(
@@ -93,7 +89,7 @@ draw_boxplot = function(range, width, varwidth, notch, outline, boxwex, staplewe
 
 
 
-data_boxplot = function() {
+data_boxplot = function(boxwex = 0.8) {
     fun = function(settings, ...) {
         env2env(settings, environment(), c("datapoints", "by", "facet", "null_facet", "null_palette", "x", "col", "bg", "null_by"))
         # Convert x to factor if it's not already
@@ -134,6 +130,20 @@ data_boxplot = function() {
         by = if (length(unique(datapoints$by)) > 1) datapoints$by else by
         facet = if (length(unique(datapoints$facet)) > 1) datapoints$facet else facet
 
+        # Compute group offsets for multi-group boxplots
+        ngrps = length(unique(datapoints$by))
+        if (ngrps > 1 && !settings$x_by) {
+            boxwex_grp = boxwex / ngrps - 0.01
+            group_offsets = seq(
+                -((boxwex - boxwex_grp) / 2),
+                ((boxwex - boxwex_grp) / 2),
+                length.out = ngrps
+            )
+        } else {
+            group_offsets = rep(0, max(ngrps, 1))
+        }
+        offsets_axis = "x"
+
         # legend customizations
         settings$legend_args[["pch"]] = settings$legend_args[["pch"]] %||% 22
         settings$legend_args[["pt.cex"]] = settings$legend_args[["pt.cex"]] %||% 3.5
@@ -150,11 +160,10 @@ data_boxplot = function() {
             "col",
             "bg",
             "by",
-            "facet"))
+            "facet",
+            "group_offsets",
+            "offsets_axis"
+        ))
     }
     return(fun)
 }
-
-
-
-

R/type_jitter.R

@@ -40,7 +40,7 @@ jitter_restore = function(obj, factor, amount) {
 
 data_jitter = function(factor, amount) {
     fun = function(settings, ...) {
-        env2env(settings, environment(), "datapoints")
+        env2env(settings, environment(), c("datapoints", "add"))
 
         x = datapoints$x
         y = datapoints$y
@@ -60,6 +60,35 @@ data_jitter = function(factor, amount) {
         } else {
             ylabs = NULL
         }
+
+        # Apply group offsets from base layer (e.g., boxplot, violin, ridge)
+        group_offsets = get_environment_variable(".group_offsets")
+        offsets_axis = get_environment_variable(".offsets_axis")
+        if (isTRUE(add) && !is.null(group_offsets)) {
+            if (identical(offsets_axis, "x") && is.factor(datapoints$by)) {
+                # x-axis offsets (boxplot, violin): keyed by group level
+                if (is.null(xlabs)) {
+                    xf = as.factor(x)
+                    xlvls = levels(xf)
+                    xlabs = seq_along(xlvls)
+                    names(xlabs) = xlvls
+                    x = as.integer(xf)
+                }
+                x = x + group_offsets[as.integer(datapoints$by)]
+            } else if (identical(offsets_axis, "y")) {
+                # y-axis offsets (ridge): keyed by y-level name
+                if (is.null(ylabs)) {
+                    yf = as.factor(y)
+                    ylvls = levels(yf)
+                    ylabs = seq_along(ylvls)
+                    names(ylabs) = ylvls
+                    y = as.integer(yf)
+                }
+                y_labels = names(ylabs)[y]
+                y = group_offsets[y_labels]
+            }
+        }
+
         x = jitter_restore(x, factor = factor, amount = amount)
         y = jitter_restore(y, factor = factor, amount = amount)
 

R/type_ridge.R

@@ -332,6 +332,11 @@ data_ridge = function(bw = "nrd0", adjust = 1, kernel = "gaussian", n = 512,
     }
     datapoints = do.call(rbind, lapply(datapoints, offset_z))
 
+    # Store y-level offsets for added layers (e.g., jitter)
+    ylevs = unique(datapoints$y)
+    group_offsets = setNames(seq_along(ylevs) - 1L, ylevs)
+    offsets_axis = "y"
+
     if (y_by) {
       datapoints$y = factor(datapoints$y)
       datapoints$by = factor(datapoints$y, levels = rev(levels(datapoints$y)))
@@ -420,7 +425,9 @@ data_ridge = function(bw = "nrd0", adjust = 1, kernel = "gaussian", n = 512,
       "datapoints",
       "yaxt",
       "ylim",
-      "type_info"
+      "type_info",
+      "group_offsets",
+      "offsets_axis"
     ))
   }
   return(fun)

R/type_violin.R

@@ -151,6 +151,19 @@ data_violin = function(bw = "nrd0", adjust = 1, kernel = "gaussian", n = 512,
             }
         }
 
+        # Compute group offsets for multi-group violins
+        if (ngrps > 1 && isFALSE(x_by) && isFALSE(facet_by)) {
+            xwidth_grp = width / ngrps - 0.01
+            group_offsets = seq(
+                -((width - xwidth_grp) / 2),
+                ((width - xwidth_grp) / 2),
+                length.out = ngrps
+            )
+        } else {
+            group_offsets = rep(0, max(ngrps, 1))
+        }
+        offsets_axis = "x"
+
         datapoints = lapply(seq_along(datapoints), function(d) {
             dat = datapoints[[d]]
             if (trim) {
@@ -182,7 +195,7 @@ data_violin = function(bw = "nrd0", adjust = 1, kernel = "gaussian", n = 512,
                 xwidth = xwidth_orig / ngrps - 0.01
                 x = rescale_num(x, to = c(0, xwidth))
                 x = x + as.numeric(sub("^([0-9]+)\\..*", "\\1", names(datapoints)[d])) - xwidth/2
-                x = x + seq(-((xwidth_orig - xwidth) / 2), ((xwidth_orig - xwidth) / 2), length.out = ngrps)[dat$by[1]]
+                x = x + group_offsets[dat$by[1]]
             } else if (nfacets > 1) {
                 x = rescale_num(x, to = c(0, xwidth))
                 x = x + as.numeric(sub("^([0-9]+)\\..*", "\\1", names(datapoints)[d])) - xwidth/2
@@ -221,9 +234,10 @@ data_violin = function(bw = "nrd0", adjust = 1, kernel = "gaussian", n = 512,
             "ylab",
             "xlabs",
             "col",
-            "bg"
+            "bg",
+            "group_offsets",
+            "offsets_axis"
         ))
     }
     return(fun)
 }
-