scatter-columns.R

# highcharter example: creating "scatter columns" with medians
# goal: scatter plot mpg by cyl, highlight medians

library(highcharter)
library(dplyr)
library(tibble)
library(purrr)

# BUILD HC DATA ------------------------------------------------
# convert to tibble
df_hc <- mtcars %>%
	rownames_to_column(var = 'car') %>%
	as_data_frame %>%
	mutate(cyl = as.character(cyl)) # make it categorical

# make marker options for median points
mrkr_opts <- list(lineColor = "#000000",
  lineWidth = 2,
  radius = 7,
  states = list(
    hover = list(
    	enabled = FALSE
  	)
	)
)

# split data by cyl
medians <- df_hc %>%
	group_by(cyl) %>%
	summarize(y = median(mpg)) %>%
	rename(name = cyl) %>%
	split(.$name)

# convert to list of data_frames to lists of HC point data
## NOTE: name convention is explicit i.e. "y", "name", "marker" follow highcharts API
## "car" DOES NOT follow the api but this data is call in the tooltip formatter
data_p50 <- medians %>%
		map(as.list) %>% # convert to list (required )
		map(append,
			list(marker = mrkr_opts, car = 'Median')) %>% # add marker data
		setNames(NULL)

data_p50 # each element of data_p50 is a point with marker characteristics

# PLOT ------------------------------------------------
# create tooltip hover that shows the car name (or median) then mpg
fmt <- JS("function() {
	return this.point.car + ': <b>' +
	this.point.y + '</b> mpg'
}")

hc <- hchart(df_hc, x = cyl, y = mpg, type = 'scatter') %>%
	hc_xAxis(categories = c("4", "6", "8")) %>% # reorder categories
	hc_add_series(data = data_p50, type = 'scatter') %>%
	hc_tooltip(formatter = fmt)
hc