Positioning of layer_text with layer_rects

[kevinykuo]

See http://stackoverflow.com/questions/24701419/heat-map-with-numbers-in-ggvis

Is this hard to fix?

[wch]

You can work around it by adding xcenter and ycenter scales:

hec <- as.data.frame(xtabs(Freq ~ Hair + Eye, HairEyeColor))

hec%>%
  ggvis(~Hair, ~Eye, fill=~Freq) %>%
  layer_rects(width = band(), height = band()) %>%
  layer_text(
    x = prop("x", ~Hair, scale = "xcenter"),
    y = prop("y", ~Eye, scale = "ycenter"),
    text:=~Freq, fontSize := 20, fill:="white", baseline:="middle", align:="center") %>%
  scale_nominal("x", padding = 0, points = FALSE) %>%
  scale_nominal("y", padding = 0, points = FALSE) %>% 
  scale_nominal("x", name = "xcenter", padding = 1, points = TRUE) %>%
  scale_nominal("y", name = "ycenter", padding = 1, points = TRUE)

In general we should have better ways of mixing centered and non-centered x/y scales. This is related to #242.