How to understand D3's paddingInner / Hongtao Hao

Hongtao Hao

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Mar 31, 2021

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How to understand D3's paddingInner

Introduction D3 practice, 2021-03-31 How to use CSS style sheets in Observable Notebooks exercise Explorable Data How to differentiate between let, const, and var in JavaScript / Observable Day 1 & Day 2, 25 Aug. & 26 Aug., 2020, Basic Commands

md`# How to understand D3's paddingInner`

d3 = require("d3@6")

viewof numBars = Range([1, 20], {value: 5, step: 1, label: "number of bars:"})

viewof paddingInner = Range([0, 1], {value: 0.6, step: 0.1, label: "paddingInner value:"})

barchart = {

const w = 900;

const h = 400;

const margin = ({top: 100, right: 15, bottom: 20, left: 25})

let dataset = [];

for (let i = 0; i < numBars; ++i) {

let randomNum = Math.random() * h;

dataset.push(randomNum)

};

let svg = d3.create("svg")

.attr("width", w)

.attr("height", h)

.style("background-color", "pink");

let xScale = d3.scaleBand()

.domain(d3.range(dataset.length))

.range([0, w])

.paddingInner(paddingInner);

let yScale = d3.scaleLinear()

.domain([0, d3.max(dataset)])

.range([0, h - margin.top]);

let bw = xScale.bandwidth()

let b = w / (numBars - paddingInner)

svg.append("text")

.attr("x", 10)

.attr("y", 20)

.text("w: "+ w +" px")

svg.append("text")

.attr("x", 10)

.attr("y", 44)

.text("p: "+ paddingInner +" ")

svg.append("text")

.attr("x", 200)

.attr("y", 20)

.text("bw (bandwidth): "+ xScale.bandwidth()+" px")

svg.append("text")

.attr("x", 200)

.attr("y", 44)

.text("wip (width of inner padding): "+ (b - bw) +" px")

svg.append("text")

.attr("x", 600)

.attr("y", 20)

.text("b (wip + bw): "+ w / (numBars - paddingInner) +" px")

svg.selectAll("rect")

.data(dataset)

.join("rect")

.attr("x", (d, i) => xScale(i))

.attr("y", d => h - yScale(d))

.attr("width", xScale.bandwidth())

.attr("height", d => yScale(d))

.style("fill", "steelblue");

return svg.node()

}

tex.block`

b = wip + bw = \frac{w}{n - p}

import {Button, Checkbox, Toggle, Radio, Range, Select, Text, Textarea, Search, Table} from "@observablehq/inputs"

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