13  Ranking

Bar charts and their variants – comparing quantities across categories.

(ns plotje-book.ranking
  (:require
   ;; Kindly -- notebook rendering protocol
   [scicloj.kindly.v4.kind :as kind]
   ;; Rdatasets -- standard datasets
   [scicloj.metamorph.ml.rdatasets :as rdatasets]
   ;; Plotje -- composable plotting
   [scicloj.plotje.api :as pj]))

(def sales {:product [:widget :gadget :gizmo :doohickey]
            :revenue [120 340 210 95]})

Count bars

pj/lay-bar with only a category column counts the rows in each category – the bar height is the number of occurrences.

Plain

Count occurrences of a categorical column.

(-> (rdatasets/datasets-iris)
    (pj/lay-bar :species))

Colored (dodged)

Grouped (dodged) bars – count by day, colored by smoking status.

(-> (rdatasets/reshape2-tips)
    (pj/lay-bar :day {:color :smoker}))

Stacked

Same data, stacked instead of dodged.

(-> (rdatasets/reshape2-tips)
    (pj/lay-bar :day {:position :stack :color :smoker}))

Proportions (100% stacked)

100% stacked bars – shows proportions instead of counts.

(-> (rdatasets/palmerpenguins-penguins)
    (pj/lay-bar :island {:position :fill :color :species}))

Horizontal

Counting bars have no native horizontal form (the category would need to be counted onto the y-axis), so flip the chart instead.

(-> (rdatasets/datasets-iris)
    (pj/lay-bar :species)
    (pj/coord :flip))

(pj/coord :flip) draws categories bottom-to-top in data order, matching ggplot2’s coord_flip(). For a ranking chart where the biggest value should appear at the top, sort the data ascending before plotting, e.g. (tc/order-by data [:value] [:asc]).

Horizontal, colored

Colored bars, flipped.

(-> (rdatasets/reshape2-tips)
    (pj/lay-bar :day {:color :time})
    (pj/coord :flip))

Value bars

Give pj/lay-bar a value column too and it uses those numbers directly as the bar heights – no counting.

Vertical

One bar per product; the bar height is the revenue.

(-> sales
    (pj/lay-bar :product :revenue))

Horizontal

Put the category on y – no coord flip needed (unlike count bars).

(-> sales
    (pj/lay-bar :revenue :product))

Rotated labels

Horizontal bars are one way to fit long category names. To keep the bars vertical instead, rotate the x-tick labels with :x-tick-angle (see Customization for details, including :x-tick-label-pad):

(-> {:department ["Office Supplies" "Electronics" "Home Goods"
                  "Sporting Gear" "Garden Tools" "Toys"]
     :revenue [120 340 210 95 160 80]}
    (pj/lay-bar :department :revenue)
    (pj/options {:x-tick-angle -45}))

Lollipop

Stem + dot – a lighter alternative to bar charts.

(-> sales
    (pj/lay-lollipop :product :revenue))

Lollipop (Horizontal)

Flipped for horizontal orientation.

(-> sales
    (pj/lay-lollipop :product :revenue)
    (pj/coord :flip))

Lollipop with :color

Map a categorical column to :color to distinguish groups visually – here, products grouped by region.

(-> {:product ["A" "B" "C" "D" "E" "F"]
     :revenue [120 95 150 80 200 110]
     :region  ["North" "South" "North" "South" "North" "South"]}
    (pj/lay-lollipop :product :revenue {:color :region}))

See Also

• Core Concepts – mappings and aesthetic vocabulary
• Distributions – when comparing categories also means comparing their distributions

What’s Next

• Change Over Time – line charts, step functions, and stacked areas
• Configuration – control dimensions, palettes, and themes

source: notebooks/plotje_book/ranking.clj