shirley wu

(@sxywu)

workshop

I'm an independent creator

of data visualizations.

Hi, I'm Shirley!

portfolio // data sketches

what we're
building today

what we'll be using

for creating

data visualizations for the web

for building

interactive single-page applications

but why use them together?

the D3 library is really big

and has a lot of functionality

raw data	→	scales	→	x / y width / height angle / radius color
raw data	→	forces hierarchies	→	x / y positions
raw data	→	geographies	→	x / y positions
raw data	→	chords shapes	→	svg path commands

brush

drag

zoom + pan

Vue's declarative rendering and reactivity system are great replacements for

D3's enter-update-exit and dispatch system

declarative rendering

<svg>
  <path v-for='d in arcs' :key='d.id' :d='d.path' :fill='d.fill' stroke='#fff' />
</svg>

const svg = d3.select('svg')

const path = svg.selectAll('path')
  .data(arcs, d => d.id);

path.exit().remove()

path.enter().append()
  .attr('stroke', '#fff')
  .merge(path)
  .attr('d', d => d.path)
  .attr('fill', d => d.fill)

reactivity system

<template>
  <svg :width='width' :height='height'>
    <path v-for='d in arcs' :d='d.path' />
  </svg>
</template>

<script>
export default {
  name: 'areachart',
  data() {
    return {
      width: 1000, height: 300,
      movies: [],
      arcs: [],
    }
  },
  watch: {
    movies() { ... }
  },
}
</script>

tells Vue to track changes for datum

when datum changes, do something

v-bind: (or :) tells Vue to automatically update if datum changes

1. translate raw data into screen space

release date → x-position
box office → y-position
metascore → color

2. calculate svg paths for drawing shapes

3. render to DOM

our custom visualization

1. translate raw data into screen space

release date → x-position
box office → y-position
metascore → color

2. calculate svg paths for drawing shapes

3. render to DOM

our custom visualization

1. d3 scales

2. d3 shapes

3. declarative rendering

scales

map from raw data (domain)

to display (range)

const width = 800
const height = 600
const data = [
  {date: new Date('01-01-2015'), boxOffice: 2349800},
  {date: new Date('01-01-2017'), boxOffice: 32487652},
  ...
]

const min = d3.min(data, d => d.date)
const max = d3.max(data, d => d.date)
const xScale = d3.scaleTime()
  .domain([min, max])
  .range([0, width])

// d3.extent returns [min, max]
const extent = d3.extent(data, d => d.boxOffice)
const yScale = d3.scaleLinear()
  .domain(extent)
  .range([height, 0])

get min/max of date
initialize time scale
pass date min/max to domain
map to min/max width in range

documentation

shapes

documentation

const data = [
  {date: new Date('01-01-2015'), boxOffice: 2349800},
  {date: new Date('01-01-2017'), boxOffice: 32487652},
  …
]

const area = d3.area()
  .x(d => xScale(d.date))
  .y1(d => yScale(d.boxOffice))
  .y0(yScale(0))

area(data)

generates SVG or Canvas path commands to draw shape