better solution to trace order; tests for density and area

Author: 13bzhang

R/trace_generation.R

@@ -276,6 +276,16 @@ layer2traces <- function(l, d, misc) {
     }
   })
 
+  # reverse the traces in the following cases:
+  # geom_area
+  # geom_density with position = stack
+  if (g$geom == "area" | 
+        g$geom == "density" & l$position$.super$objname == "stack"){
+    traces <- rev(traces)
+  } else{
+    traces
+  }
+  
   ord <- order(sort.val)
   no.sort <- traces[ord]
   for(tr.i in seq_along(no.sort)){

tests/testthat/test-ggplot-area.R

@@ -26,3 +26,41 @@ test_that("transparency alpha in geom_area is converted", {
 })
 
 save_outputs(gg, "area-fillcolor")
+
+# Test that the order of traces is correct
+# Expect traces function
+expect_traces <- function(gg, n_traces, name) {
+  stopifnot(is.ggplot(gg))
+  stopifnot(is.numeric(n_traces))
+  save_outputs(gg, paste0("coord_fixed-", name))
+  L <- gg2list(gg)
+  all_traces <- L$data
+  no_data <- sapply(all_traces, function(tr) {
+    is.null(tr[["x"]]) && is.null(tr[["y"]])
+  })
+  has_data <- all_traces[!no_data]
+  expect_equal(length(has_data), n_traces)
+  list(traces = has_data, layout = L$layout)
+}
+# Generate ggplot object
+library(dplyr)
+df <- diamonds %>% group_by(carat, cut) %>% 
+  summarise(n = n()) %>% mutate(freq = n/sum(n))
+df$r.cut <- factor(df$cut, levels = rev(levels(df$cut)))
+p <- ggplot(data = df, aes(x = carat, y = freq, fill = cut)) + 
+  geom_area() 
+# Test 
+test_that("traces are ordered correctly in geom_area", {
+  info <- expect_traces(p, 5, "geom_area_traces_order")
+  tr <- info$traces[[1]]
+  la <- info$layout
+  expect_identical(tr$type, "scatter")
+  # check trace order
+  trace.names <- rev(levels(df$cut))
+  for (i in 1:5){
+    expect_identical(info$traces[[i]]$name, trace.names[i])
+  }
+})
+# Save output
+save_outputs(p, "area_traces_order")
+

tests/testthat/test-ggplot-density.R

@@ -54,3 +54,23 @@ test_that("geom_histogram(aes(y = ..density..)) + geom_density() works", {
   type <- unique(sapply(trs, "[[", "type"))
   expect_identical(sort(type), c("bar", "scatter"))
 })
+
+# Check if the traces are in the correct order when position = stack
+# Generate ggplot object
+p <- ggplot(data = movies, aes(x = rating, fill = mpaa,)) + 
+  geom_density(position = "stack")
+# Test 
+test_that("traces are ordered correctly in geom_density", {
+  info <- expect_traces(p, 5, "geom_density_traces_order")
+  tr <- info$traces[[1]]
+  la <- info$layout
+  expect_identical(tr$type, "scatter")
+  # check trace order
+  trace.names <- rev(levels(movies$mpaa))
+  for (i in 1:5){
+    expect_identical(info$traces[[i]]$name, trace.names[i])
+  }
+})
+# Save output
+save_outputs(p, "density_traces_order")
+