Echarts4r polar barchart can't show a third data field in the tooltip

Question

I was trying to create a polar barchart with the echarts4r library and the chart is generated properly. I have x, y, and z fields in the dataset. To generate the chart we need only the x and y fields. Now I want to show x, y and z in the tooltip. x and yare showing well in the tooltip, however the z value is undefined. See below an example code:

library(echarts4r)

# create example dataset
df <- data.frame(x = c("A", "B", "C"), y = c(10, 20, 30), z = c("foo", "bar", "baz"))

# create polar bar chart
df %>%
  e_charts(x) %>%
  e_bar(y, coord_system = "polar") %>%
  e_angle_axis(startAngle = 90, max = 150, axisLine = list(show = FALSE), axisTick = list(show = FALSE),
               splitLine = list(show = FALSE), axisLabel = list(show = FALSE)) %>%
  e_radius_axis(type = "category", data = df$x, axisLabel = list(interval =0,margin = 50, fontSize= 15, color = 'black'),
                axisLine = list(show = FALSE), axisTick = list(show = FALSE), z = 10) %>% 
  e_polar() %>%
  e_legend(show = FALSE) %>%
  e_tooltip(formatter = htmlwidgets::JS("
    function(params) {
      return params.name + '<br>' + params.value + '<br>' + params.data.z;
    }
  "))

How can I also show the z value in the tooltip?

Answer 1

You first have to include the values of z into your chart. This is usually not very difficult using e_add_nested(), however, there seems to be a bug in combination with e_polar().

In order to get it work, I used the fix_add_nested function from this very good answer. If you include this, you can access the z values using params.data.itemStyle.z.

library(echarts4r)

# create example dataset
df <- data.frame(x = c("A", "B", "C"), y = c(10, 20, 30), z = c("foo", "bar", "baz"))

fix_add_nested <- function(e) {
    e$x$opts$series[[1]]$data <- lapply(
        e$x$opts$series[[1]]$data, 
        function(x) { names(x) <- c("value", "itemStyle"); x }
    )
    
    e
}

# create polar bar chart
df %>%
    e_charts(x) %>%
    e_bar(y, coord_system = "polar") %>%
    e_angle_axis(startAngle = 90, max = 150, axisLine = list(show = FALSE), axisTick = list(show = FALSE),
                 splitLine = list(show = FALSE), axisLabel = list(show = FALSE)) %>%
    e_radius_axis(type = "category", data = df$x, axisLabel = list(interval =0,margin = 50, fontSize= 15, color = 'black'),
                  axisLine = list(show = FALSE), axisTick = list(show = FALSE), z = 10) %>% 
    e_polar() %>%
    e_legend(show = FALSE) %>%
    e_add_nested("values", z) %>%
    fix_add_nested() %>% 
    e_tooltip(formatter = htmlwidgets::JS("
    function(params) {
      return params.name + '<br>' + params.value + '<br>' + params.data.itemStyle.z;
    }
    "))