Week 6 - World Heritage Sites
(ns tidy-tuesdays.2024.week06.heritage
(:require
[scicloj.kindly.v4.kind :as kind]))Introduction
This week the challenge is to work with a small dataset and produce interesting visualisations. This is a great exercise for me personally, because so far (in my work with clojure and data) I have been more interested in processing and exploring the data, and I tent to be a bit ‘lazy’ when it comes to details around the visualisations and aesthetics
To start with, here is the simple dataset we are working with:
(kind/table
{:column-names ["Country" "2004" "2022"]
:row-maps [{"Country" "Norway" "2004" 5 "2022" 8}
{"Country" "Denmark" "2004" 4 "2022" 10}
{"Country" "Sweeden" "2004" 13 "2022" 15}]})| Country | 2004 | 2022 |
|---|---|---|
| Norway | 5 | 8 |
| Denmark | 4 | 10 |
| Sweeden | 13 | 15 |
Basic Bar Chart
Let’s start with a basic bar chart, but I want to try make it a bit ‘tidier’ and include a nice title/subtitle (using thing repo as a reference point - https://github.com/aezarebski/vegacookbook.
First, I will restucture the data a bit (to make it fit only way I know how to do ‘grouped’ bar charts…)
(def heritage-sites
[{:country "Norway" :value 5 :year 2004}
{:country "Norway" :value 8 :year 2022}
{:country "Denmark" :value 4 :year 2004}
{:country "Denmark" :value 10 :year 2022}
{:country "Sweeden" :value 13 :year 2004}
{:country "Sweeden" :value 15 :year 2022}])(kind/vega
{:$schema "https://vega.github.io/schema/vega-lite/v5.json"
:data {:values heritage-sites}
:mark :bar
:height 400
:width 100
:encoding {:column {:field :country
:type :ordinal
:title nil
:header {:labelOrient :bottom}}
:x {:field :year
:type :ordinal
:title nil
:axis {:labels false
:ticks false}}
:y {:field :value
:type :quantitative
:title nil
:axis {:grid true
:domain false}}
:color {:field :year
:type :ordinal
:title nil
:scale {:range ["#1380A1" "#FAAB18"]}}}
:config {:view {:stroke :transparent}
:legend {:orient :top}}
:title {:text "A Richer Heritage"
:subtitle "Number of World Heritage Sites, 2004-2022"}})An alternative bar chart
The same chart as above, but with ‘circle’ marks instead of bars…
First, expand the data:
(def heritage-sites-v2
(reduce (fn [acc {:keys [country value year]}]
(into acc
(for [offset (range value)]
{:country country
:year year
:offset (inc offset)})))
[]
heritage-sites))Then, the chart:
(kind/vega
{:$schema "https://vega.github.io/schema/vega-lite/v5.json"
:data {:values heritage-sites-v2}
:mark {:type "circle" :size 250}
:height 280
:width 100
:encoding {:column {:field :country
:type :ordinal
:title nil
:header {:labelOrient :bottom}}
:x {:field :year
:type :ordinal
:title nil
:axis {:labels false
:ticks false}}
:y {:field :offset
:type :quantitative
:title nil
:axis {:grid true
:domain false}}
:color {:field :year
:type :ordinal
:title nil
:scale {:range ["#a6639c" "#3a417c"]}}}
:config {:view {:stroke :transparent}
:legend {:orient :top}}
:title {:text "A Richer Heritage"
:subtitle "Number of World Heritage Sites, 2004-2022"}})A donut chart
Finally, I tried to make a pie/doughnut chart version of the data. This mostly involved lots of tweaking with vega lite properties with no clear sense of where I was going! A lot of complexity and effort involved for something quite simple, and also something which in the end is not very reusable. I don’t know much about Vega Lite at all yet, so a better way to do this would be to automatically calculate some of the angles, etc., instead of hard-coding the values like I’ve done.
To make this chart I first made the ‘circle’ elements (half-circles):
(defn circle [year inner-radius outer-radius range-min range-max]
{:data {:values (->> heritage-sites-v2
(reduce (fn [acc m]
(conj acc (assoc m :offset 1)))
[])
(filter #(= year (:year %))))}
:mark {:type :arc
:radius outer-radius
:radius2 inner-radius
:cornerRadius 10
:padAngle 0.009}
:encoding {:theta {:field :offset
:type :quantitative
:scale {:type "linear" :rangeMax range-max :rangeMin range-min}}
:color {:field :country
:type :nominal
:scale {:range ["#efe6d5" "#9dbeb7" "#e73213"]}}}})Then, the ‘label’ elements (“2004” and “2022”)
(defn label [label radius theta angle]
{:mark {:type :text
:radius radius
:theta theta
:angle angle
:color "gray"
:fontSize 18}
:encoding {:text {:value label}}})Finally, putting it together as a chart:
(kind/vega
{:$schema "https://vega.github.io/schema/vega-lite/v5.json"
:data {:values {}} ;; I'm not sure why, but this is needed for the 'labels' to appear...
:height 320
:layer [(circle 2004 60 100 -3.0708 0)
(label "2004" 80 5.4 37)
(circle 2022 110 150 -3.0708 0)
(label "2022" 130 0.1 90)]
:config {:legend {:title ""
:direction :horizontal
:orient :bottom}}
:title {:text "A Richer Heritage"
:subtitle "Number of World Heritage Sites, 2004-2022"}})The same chart, rotated:
(kind/vega
{:$schema "https://vega.github.io/schema/vega-lite/v5.json"
:data {:values {}} ;; I'm not sure why, but this is needed for the 'labels' to appear...
:height 320
:layer [(circle 2004 60 100 1.55 -1.47)
(label "2004" 80 5.65 64)
(circle 2022 110 150 1.55 -1.47)
(label "2022" 130 4.7 0)]
:config {:legend {:title ""
:direction :horizontal
:orient :top}}
:title {:text "A Richer Heritage"
:subtitle "Number of World Heritage Sites, 2004-2022"}})