Maps, Data, Viz, UX, Design
chart = {
const svg = d3.select(DOM.svg(width, h))
.classed("crashes-heatmap", true)
// code credit: https://observablehq.com/@tmcw/d3-scalesequential-continuous-color-legend-example
// and: https://www.visualcinnamon.com/2016/05/smooth-color-legend-d3-svg-gradient.html
const defs = svg.append("defs");
const linearGradient = defs.append("linearGradient")
.attr("id", "linear-gradient");
linearGradient.selectAll("stop")
.data(color.ticks().map((t, i, n) => ({ offset: `${100*i/n.length}%`, color: color(t) })))
.enter().append("stop")
.attr("offset", d => d.offset)
.attr("stop-color", d => d.color);
const g = svg.append("g")
.attr("transform", `translate(${margin.left}, ${margin.top})`)
g.selectAll("rect")
.data(data)
.enter().append("rect")
.attr("x", d => d.hour * gridSize)
.attr("y", d => d.day * gridSize)
.attr("width", gridSize)
.attr("height", gridSize)
.attr("fill", d => color(d.value))
.attr("stroke", "#e2e2e2")
.append("title")
.text(d => d.value)
g.selectAll(".day")
.data(days)
.enter().append("text")
.text(d => d)
.classed("day", true)
.attr("x", 0)
.attr("y", (d, i) => i * gridSize)
.style("text-anchor", "end")
.attr("transform", "translate(-6," + gridSize / 1.5 + ")")
g.selectAll(".hour")
.data(hours)
.enter().append("text")
.text(d => d)
.classed("hour", true)
.attr("x", (d, i) => i * gridSize)
.attr("y", 0)
.style("text-anchor", "middle")
.attr("transform", "translate(" + gridSize / 2 + ", -6)");
g.append("g")
.call(legend)
return svg.node();
}
margin = ({ top: 40, right: 50, bottom: 70, left: 50 })
w = width - margin.left - margin.right
gridSize = Math.floor(w / hours.length )
h = gridSize * days.length + margin.top + margin.bottom
days = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"]
hours = d3.range(24)
color = d3
.scaleSequential()
.domain([0, d3.max(data, d => d.value)])
.interpolator(t => d3.interpolateViridis(1 - t)) // reverses the color ramp
legend = g => {
g.attr("transform", `translate(0, ${h - margin.bottom - legendBarHeight })`)
.append("rect")
.attr("width", w)
.attr("height", legendBarHeight)
.style("fill", "url(#linear-gradient)")
g.call(axisBottom)
}
axisScale = d3.scaleLinear()
.domain(color.domain())
.range([0, w])
axisBottom = g => {
g.classed("axis axis--bottom", true)
.attr("transform", `translate(0, ${h - margin.bottom - legendBarHeight})`)
.call(d3.axisBottom(axisScale)
.ticks(width / 80)
.tickSize(legendBarHeight))
.select(".domain")
.remove()
}
legendBarHeight = 10
css = html`<style>
svg.crashes-heatmap text {
font-family: sans-serif;
font-size: 12px;
fill: #333;
}
svg.crashes-heatmap .axis.axis--bottom line {
stroke: #fff;
}
</style>`
query = sls`
SELECT
EXTRACT(HOUR FROM c.date_val) as hour,
EXTRACT(DOW FROM c.date_val) as day,
c.number_of_persons_injured as value
FROM crashes_all_prod c
WHERE
( year::text || LPAD(month::text, 2, '0') <= '2019' || LPAD(3::text, 2, '0') ) AND
( year::text || LPAD(month::text, 2, '0') >= '2019' || LPAD(1::text, 2, '0') ) AND
( number_of_persons_injured > 0 )
GROUP BY hour, day, value
ORDER BY day, hour, value
`
url = `https://chekpeds.carto.com/api/v2/sql?q=${encodeURIComponent(query)}&format=CSV`
data = {
try {
return await d3.csv(url, parseRow);
} catch (e) {
throw new Error(`Something went wrong: ${e.message}`)
}
}
parseRow = d => {
Object.keys(d).forEach(key => d[key] = +d[key])
return d;
}
d3 = require("d3@5")
sls = require('https://bundle.run/single-line-string@0.0.2')
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