ggvis with tooltip not working with layer_smooths

Question

This code works as expected:

all_values <- function(x) {
  if(is.null(x)) return(NULL)
  row <- mtc[mtc$id == x$id, ]
  paste0(names(row), ": ", format(row), collapse = "<br />")
}

mtc %>% ggvis(x = ~wt, y = ~mpg, key := ~id) %>%
  layer_points() %>%
  add_tooltip(all_values, "hover")

but when I add layer_smooths(stroke := "red", se = T) the code give me an error:

mtc %>% ggvis(x = ~wt, y = ~mpg, key := ~id) %>%
  layer_points() %>%
  layer_smooths(stroke := "red", se = T) %>%
  add_tooltip(all_values, "hover")

Error in eval(expr, envir, enclos) : object 'id' not found

Why? how can I fix it?

Thanks!

Answer 1

If I hadn't recognized this as an example from one of the ggvis help pages, I wouldn't have known where mtc came from. The problem seems to be that you set the key property in the ggvis() statement, but layer_smooths() evidently doesn't support it, so you need to move it into layer_points(). I got the visualization to run with the following code:

library(ggvis)
mtc <- mtcars
mtc$id <- seq_len(nrow(mtc))

all_values <- function(x) 
 {
   if(is.null(x)) return(NULL)
   row <- mtc[mtc$id == x$id, ]
   paste0(names(row), ": ", format(row), collapse = "<br />")
 }

mtc %>% ggvis(x = ~wt, y = ~mpg) %>%
  layer_smooths(stroke := "red", se = T) %>%
  layer_points(key := ~id) %>%
  add_tooltip(all_values, "hover")

However, when you hover over the smooth or the confidence bands, all of the values associated with the variables are labeled 'character(0)' in the tooltip.