x = d3.scalePoint(attributes, [margin.left, width - margin.right])
y = {
let scales = new Map();
// TODO: create a suitable scale for each attribute and add it to the map
attributes.forEach(function(attribute) {
if (attribute == "origin") {
scales.set(
attribute,
d3.scaleOrdinal().domain(d3.map(data, d => d[attribute])).range([height - margin.bottom, height/2, margin.top])
);
}
else {
scales.set(
attribute,
d3.scaleLinear().domain(d3.extent(data, d => d[attribute])).range([height - margin.bottom, margin.top])
);
}
});
return scales;
}
paracoords = {
const svg = d3.create("svg").attr("viewBox", [0, 0, width, height]);
// set the style of hidden data items
svg
.append("style")
.text("path.hidden { stroke: #000; stroke-opacity: 0.01;}");
// a map that holds any active brush per attribute
let activeBrushes = new Map();
const polylines = svg
.append("g")
.attr("fill", "none")
.attr("stroke-width", 1.5)
.attr("stroke-opacity", 0.4)
.selectAll("path")
.data(data)
.join("path")
// TODO: create the polylines
.attr("d", d => d3.line()
.curve(d3.curveCatmullRom)
.defined(([, value]) => value != null)
.y(([key, value]) => y.get(key)(value))
.x(([key]) => x(key))
(d3.cross(attributes, [d], (key, d) => [key, d[key]])))
// TODO: apply the color scale from task 3
.attr("stroke", d => col(d[colorAttribute])); // col is a function created in appendix
// create the group nodes for the axes
const axes = svg
.append("g")
.selectAll("g")
.data(attributes)
.join("g")
.attr("transform", d => `translate(${x(d)},0)`)
// TODO: add the visual representation of the axes
.each(function(d) { d3.select(this).call(d3.axisRight(y.get(d))); })
.call(g => g.append("text")
.attr("y", margin.bottom - 5)
.attr("x", -5)
.attr("text-anchor", "start")
.attr("fill", "currentColor")
.text(d => shortAttributeNames.get(d)))
.call(g => g.selectAll("text")
.clone(true).lower()
.attr("fill", "none")
.attr("stroke-width", 5)
.attr("stroke-linejoin", "round")
.attr("stroke", "white"));
function updateBrushing() {
// TODO implement brushing & linking
polylines.classed("hidden", d => {
var hidden;
attributes.forEach(function(key) {
if (!activeBrushes.has(key)) return;
else if (activeBrushes.get(key) === null) return;
else {
const [y0,y1] = activeBrushes.get(key);
if (!hidden) {
hidden = y0 > y.get(key)(d[key]) ||
y1 < y.get(key)(d[key])
}
};
});
return hidden;
});
}
function brushed(attribute) {
activeBrushes.set(attribute, d3.event.selection);
updateBrushing();
}
function brushEnd(attribute) {
if (d3.event.selection !== null) return;
activeBrushes.delete(attribute);
updateBrushing();
}
const brushes = axes.append("g").call(
d3
.brushY()
.extent([[-10, margin.top], [10, height - margin.bottom]])
.on("brush", brushed)
.on("end", brushEnd)
);
return svg.node();
}
md`## Appendix`
height = 500
margin = ({ top: 20, right: 30, bottom: 20, left: 20 })
data = d3.csvParse(await FileAttachment("cars.csv").text(), d3.autoType)
attributes = data.columns.filter(d => d !== "name")
shortAttributeNames = new Map(
Object.entries({
mpg: "MPG",
cylinders: "CYL",
displacement: "DPL",
horsepower: "HP",
weight: "WGT",
acceleration: "ACL",
year: "YEAR",
origin: "OGN"
})
)
// function created for assigning colors
col = ((colorAttribute == "origin") ? d3.scaleOrdinal(d3.schemeCategory10).domain(y.get(colorAttribute).domain().reverse()) : d3.scaleSequential().domain(y.get(colorAttribute).domain().reverse()).interpolator(d3.interpolateInferno))
import { select } from "@jashkenas/inputs"
d3 = require("d3@5")
Purpose-built for displays of data
Observable is your go-to platform for exploring data and creating expressive data visualizations. Use reactive JavaScript notebooks for prototyping and a collaborative canvas for visual data exploration and dashboard creation.
