How to change the min/max values for the visual map in echarts4r

Question

According to this, I thought I could change the max value shown in the visual map like so:

e_visual_map(value, max = 100) 

But this seems to have no effect.

Here is a full example:

library(echarts4r)

# Sample data
df <- data.frame(
  category = c("Low Avg", "High Avg", "Low Avg", "High Avg"),
  max = c("Low Max", "High Max", "High Max", "Low Max"),
  value = c(10, 40, 20, 30) # replace with your actual values
)

df |>
  e_charts(category) |>
  e_heatmap(max, value, ) |>
  e_visual_map(value, max = 100) |>
  e_x_axis(max, type = "category") |>
  e_y_axis(category, type = "category")

I expect the slider max value to be 100 instead of 40.

Answer 1

Not sure whether this is intended or whether this is a bug. After a look at the source the issue is that when you pass a serie to e_visual_map the min and max values are set according to range of the data:

https://github.com/JohnCoene/echarts4r/blob/8f1d2ea10504c3aa0f77cc1bff91526ed7b6967f/R/opts.R#L109

Hence, your max value will have no effect as it gets overwritten.

One option would be to not pass the name of the serie to e_visual_map in which case the max value does get set or overwritten

df |>
  e_charts(category) |>
  e_heatmap(max, value, ) |>
  e_visual_map(max = 100) |>
  e_x_axis(max, type = "category") |>
  e_y_axis(category, type = "category")

A second option would be to pass a scale function to the scale argument:

library(echarts4r)

df |>
  e_charts(category) |>
  e_heatmap(max, value) |>
  e_visual_map(value, scale = function(x) scales::rescale(x, to = c(0, 100))) |>
  e_x_axis(max, type = "category") |>
  e_y_axis(category, type = "category")