Published
Edited
Jun 9, 2020
4 forks
x = d3.scalePoint(attributes, [margin.left, width - margin.right])
y = {
let scales = new Map();
attributes.forEach(function(attribute) {
//only attribute origin is ordinal data and needs a different scale
if (attribute == "origin"){
scales.set(
attribute,
//https://observablehq.com/@sophiegri/exercise-2-scatterplot-matrix
//d3.extent gets min and max value of the given attribute
//3 attributes for origin so axis needs to be cut in half
d3.scaleOrdinal().range([height - margin.bottom, height/2, margin.top])
.domain(d3.extent(data, item => item[attribute]))
);
}
else {
scales.set(
attribute,
//d3.extent gets min and max value of the given attribute
d3.scaleLinear().range([height - margin.bottom, margin.top])
.domain(d3.extent(data, item => item[attribute]))
);
}
});
return scales;
}
//https://observablehq.com/@sophiegri/exercise-2-scatterplot-matrix
color = d3.scaleOrdinal(d3.schemeTableau10)
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")
//paint the polylines
//https://observablehq.com/@sophiegri/exercise-2-scatterplot-matrix
.attr("stroke", d => color(d[colorAttribute]))
//set the lines
//https://observablehq.com/@d3/parallel-coordinates
.attr("d", d => d3.line()
.defined(([, value]) => value != null)
.y(([key, value]) => y.get(key)(value))
.x(([key]) => x(key))
(d3.cross(attributes, [d], (key, d) => [key, d[key]])));
// 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)`)
//https://observablehq.com/@d3/parallel-coordinates
//set axis to the right and set the text
.each(function(d) { d3.select(this).call(d3.axisRight(y.get(d))); })
.call(g => g.append("text")
//position of the text
.attr("x", -1)
.attr("y", 7.5)
.attr("text-anchor", "start")
.attr("fill", "currentColor")
//.get(d) gets the short name (value) from the Map shortAttributeNames
.text(d => shortAttributeNames.get(d)));
function updateBrushing() {
var number_brushes = activeBrushes.size;
if (number_brushes == 0) {
//false is colored, true is hidden
polylines.classed("hidden", d => {return false});
}
else {
polylines.classed("hidden", d => {
var return_value = false;
//iterate over Map and get y-values
activeBrushes.forEach((value, key) => {
var y0 = value[0];
var y1 = value[1];
//check if car value is inside an active brush
var value_y = y.get(key)(d[key]);
if (value_y <= y1 && value_y >= y0) {
}
else {
return_value=true;
}
});
//variable to see the active polylines in this scope
return return_value;
});
}
}
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: 10, right: 30, bottom: 10, left: 10 })
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"
})
)
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.
