convert factor x/y to numeric in type_text

NEWS.md

@@ -38,6 +38,8 @@ where the formatting is also better._
      bug report in #449.
   - Numeric labellers now work on appropriate `x`/`y` variables, even if the
     plot type internally coerces it to factor (e.g., `"boxplot"`)
+- `type_text()` can now also deal with factor `x`/`y` variables by converting
+  them to numeric which helps to add text to barplots etc. (#470 @zeileis)
 
 
 ### Internals

R/type_text.R

@@ -51,6 +51,8 @@ data_text = function(labels, clim = c(0.5, 2.5)) {
       stop(msg, call. = FALSE)
     }
     datapoints$labels = labels
+    if (is.factor(datapoints$x)) datapoints$x = as.numeric(datapoints$x)
+    if (is.factor(datapoints$y)) datapoints$y = as.numeric(datapoints$y)
 
     # browser()
     bubble = FALSE

inst/tinytest/test-type_barplot.R

@@ -45,3 +45,11 @@ f = function() {
   tinyplot(~ cyl, data = mtcars, type = "barplot", xlevels = 3:1)
 }
 expect_snapshot_plot(f, label = "barplot_xlevels_issue430")
+
+f = function() {
+  tab = as.data.frame(xtabs(~ cyl, data = mtcars))
+  tinyplot(Freq ~ cyl, data = tab, type = "barplot")
+  tinyplot_add(type = "text", labels = tab$Freq, pos = 3, xpd = TRUE)
+}
+expect_snapshot_plot(f, label = "barplot_text_issue469")
+