R使用highcharter绘制地图时tooltip无法读取dataframe数值问题

问题原因 #

你在hc_add_series_map中通过value参数指定的数值字段，会被Highcharts默认映射为点对象的value属性，不会保留原字段名occurences挂载到this.point下，因此直接读取this.point.occurences会返回空值。

解决方案 #

只需要修改hc_tooltip中JS格式化函数的取值字段，把this.point.occurences替换为this.point.value即可，同时修正你代码中hc_tooltip结尾的管道符笔误（缺了>）。

修改后完整可运行代码如下：

library(httr)
library(highcharter)
library(scales)

map <- "https://code.highcharts.com/mapdata/custom/world-highres.geo.json" %>% 
  GET() %>% 
  content() %>% 
  jsonlite::fromJSON(simplifyVector = FALSE)

sample_table <- data.frame(name = c("Spain","France","China"),
                           continent = c("Europe","Europe","Asia"),
                           occurences = c(150,70,120))

cols3 <- scales::viridis_pal(option = "turbo",
                             begin = 0.4,
                             direction = 1)(length(unique(sample_table$name)))

highchart(type = "map") %>% 
  hc_title(text = "Map Title") %>%
  hc_subtitle(text = "Map Subtitle") %>%
  hc_add_series_map(map = map, df = sample_table, joinBy = "name", value = "occurences",
                    dataLabels = list(enabled = TRUE
                                      ,format = "{point.properties.hc-a2}")
  ) %>%
  hc_colors(cols3) %>%
  hc_colorAxis(stops = color_stops(colors = cols3)) %>%
  hc_tooltip(
    useHTML = TRUE,                             
    formatter = JS(
      "
      function(){
        outHTML = '<b>' + this.point.name + '</b> <br>' + this.point.continent +
        '</b> <br>' + this.point.value
        return(outHTML)
      }

      "
    )) %>%
  hc_mapNavigation(enabled = TRUE)

修改后tooltip可正常显示数值，效果参考：

拓展：如需保留原字段名访问 #

如果需要在JS中直接通过this.point.occurences访问数值，可在hc_add_series_map中添加keys参数显式声明要保留的字段：

hc_add_series_map(map = map, df = sample_table, joinBy = "name", value = "occurences",
                  keys = c("name", "continent", "occurences"),
                  dataLabels = list(enabled = TRUE,format = "{point.properties.hc-a2}")
)

这种场景下不需要修改formatter的原有取值逻辑，也能正常读取occurences字段。

内容的提问来源于stack exchange，提问作者James