Bar
Since we want an ordinal y-axis and Layer Cake defaults to a linear scale, pass in a custom scale to yScale
with a few formatting options. Set the x-scale to always start at 0
so you don't show misleading differences between groups.
- +page.svelte
- ./_components/Bar.svelte
- ./_components/AxisX.svelte
- ./_components/AxisY.svelte
- ./_data/groups.csv
<script>
import { LayerCake, Svg } from 'layercake';
import { scaleBand } from 'd3-scale';
import Bar from './_components/Bar.svelte';
import AxisX from './_components/AxisX.svelte';
import AxisY from './_components/AxisY.svelte';
// This example loads csv data as json and converts numeric columns to numbers using @rollup/plugin-dsv. See vite.config.js for details
import data from './_data/groups.csv';
const xKey = 'value';
const yKey = 'year';
</script>
<div class="chart-container">
<LayerCake
padding={{ bottom: 20, left: 35 }}
x={xKey}
y={yKey}
yScale={scaleBand().paddingInner(0.05)}
xDomain={[0, null]}
{data}
>
<Svg>
<AxisX tickMarks baseline snapLabels />
<AxisY tickMarks gridlines={false} />
<Bar />
</Svg>
</LayerCake>
</div>
<style>
/*
The wrapper div needs to have an explicit width and height in CSS.
It can also be a flexbox child or CSS grid element.
The point being it needs dimensions since the <LayerCake> element will
expand to fill it.
*/
.chart-container {
width: 100%;
height: 250px;
}
</style>
<!--
@component
Generates an SVG bar chart.
-->
<script>
import { getContext } from 'svelte';
const { data, xGet, yGet, xScale, yScale } = getContext('LayerCake');
/**
* @typedef {Object} Props
* @property {string} [fill='#00bbff'] - The shape's fill color. This is technically optional because it comes with a default value but you'll likely want to replace it with your own color.
*/
/** @type {Props} */
let { fill = '#00bbff' } = $props();
</script>
<g class="bar-group">
{#each $data as d, i}
<rect
class="group-rect"
data-id={i}
x={$xScale.range()[0]}
y={$yGet(d)}
height={$yScale.bandwidth()}
width={$xGet(d)}
{fill}
></rect>
{/each}
</g>
<!--
@component
Generates an SVG x-axis. This component is also configured to detect if your x-scale is an ordinal scale. If so, it will place the markers in the middle of the bandwidth.
-->
<script>
import { getContext } from 'svelte';
const { width, height, xScale, yRange } = getContext('LayerCake');
/**
* @typedef {Object} Props
* @property {boolean} [tickMarks=false] - Show a vertical mark for each tick.
* @property {boolean} [gridlines=true] - Show gridlines extending into the chart area.
* @property {number} [tickMarkLength=6] - The length of the tick mark.
* @property {boolean} [baseline=false] - Show a solid line at the bottom.
* @property {boolean} [snapLabels=false] - Instead of centering the text labels on the first and the last items, align them to the edges of the chart.
* @property {(d: any) => string} [format=d => d] - A function that passes the current tick value and expects a nicely formatted value in return.
* @property {number|Array<any>|Function} [ticks] - If this is a number, it passes that along to the [d3Scale.ticks](https://github.com/d3/d3-scale) function. If this is an array, hardcodes the ticks to those values. If it's a function, passes along the default tick values and expects an array of tick values in return. If nothing, it uses the default ticks supplied by the D3 function.
* @property {number} [tickGutter=0] - The amount of whitespace between the start of the tick and the chart drawing area (the yRange min).
* @property {number} [dx=0] - Any optional value passed to the `dx` attribute on the text label.
* @property {number} [dy=12] - Any optional value passed to the `dy` attribute on the text label.
*/
/** @type {Props} */
let {
tickMarks = false,
gridlines = true,
tickMarkLength = 6,
baseline = false,
snapLabels = false,
format = d => d,
ticks = undefined,
tickGutter = 0,
dx = 0,
dy = 12
} = $props();
/** @param {number} i
* @param {boolean} sl */
function textAnchor(i, sl) {
if (sl === true) {
if (i === 0) {
return 'start';
}
if (i === tickVals.length - 1) {
return 'end';
}
}
return 'middle';
}
let tickLen = $derived(tickMarks === true ? (tickMarkLength ?? 6) : 0);
let isBandwidth = $derived(typeof $xScale.bandwidth === 'function');
/** @type {Array<any>} */
let tickVals = $derived(
Array.isArray(ticks)
? ticks
: isBandwidth
? $xScale.domain()
: typeof ticks === 'function'
? ticks($xScale.ticks())
: $xScale.ticks(ticks)
);
let halfBand = $derived(isBandwidth ? $xScale.bandwidth() / 2 : 0);
</script>
<g class="axis x-axis" class:snapLabels>
{#each tickVals as tick, i (tick)}
{#if baseline === true}
<line class="baseline" y1={$height} y2={$height} x1="0" x2={$width} />
{/if}
<g class="tick tick-{i}" transform="translate({$xScale(tick)},{Math.max(...$yRange)})">
{#if gridlines === true}
<line class="gridline" x1={halfBand} x2={halfBand} y1={-$height} y2="0" />
{/if}
{#if tickMarks === true}
<line
class="tick-mark"
x1={halfBand}
x2={halfBand}
y1={tickGutter}
y2={tickGutter + tickLen}
/>
{/if}
<text x={halfBand} y={tickGutter + tickLen} {dx} {dy} text-anchor={textAnchor(i, snapLabels)}
>{format(tick)}</text
>
</g>
{/each}
</g>
<style>
.tick {
font-size: 11px;
}
line,
.tick line {
stroke: #aaa;
stroke-dasharray: 2;
}
.tick text {
fill: #666;
}
.tick .tick-mark,
.baseline {
stroke-dasharray: 0;
}
/* This looks slightly better */
.axis.snapLabels .tick:last-child text {
transform: translateX(3px);
}
.axis.snapLabels .tick.tick-0 text {
transform: translateX(-3px);
}
</style>
<!--
@component
Generates an SVG y-axis. This component is also configured to detect if your y-scale is an ordinal scale. If so, it will place the tickMarks in the middle of the bandwidth.
-->
<script>
import { getContext } from 'svelte';
const { xRange, yScale, width } = getContext('LayerCake');
/**
* @typedef {Object} Props
* @property {boolean} [tickMarks=false] - Show marks next to the tick label.
* @property {string} [labelPosition='even'] - Whether the label sits even with its value ('even') or sits on top ('above') the tick mark. Default is 'even'.
* @property {boolean} [snapBaselineLabel=false] - When labelPosition='even', adjust the lowest label so that it sits above the tick mark.
* @property {boolean} [gridlines=true] - Show gridlines extending into the chart area.
* @property {number} [tickMarkLength] - The length of the tick mark. If not set, becomes the length of the widest tick.
* @property {(d: any) => string} [format=d => d] - A function that passes the current tick value and expects a nicely formatted value in return.
* @property {number|Array<any>|Function} [ticks=4] - If this is a number, it passes that along to the [d3Scale.ticks](https://github.com/d3/d3-scale) function. If this is an array, hardcodes the ticks to those values. If it's a function, passes along the default tick values and expects an array of tick values in return.
* @property {number} [tickGutter=0] - The amount of whitespace between the start of the tick and the chart drawing area (the xRange min).
* @property {number} [dx=0] - Any optional value passed to the `dx` attribute on the text label.
* @property {number} [dy=0] - Any optional value passed to the `dy` attribute on the text label.
* @property {number} [charPixelWidth=7.25] - Used to calculate the widest label length to offset labels. Adjust if the automatic tick length doesn't look right because you have a bigger font (or just set `tickMarkLength` to a pixel value).
*/
/** @type {Props} */
let {
tickMarks = false,
labelPosition = 'even',
snapBaselineLabel = false,
gridlines = true,
tickMarkLength = undefined,
format = d => d,
ticks = 4,
tickGutter = 0,
dx = 0,
dy = 0,
charPixelWidth = 7.25
} = $props();
/** @param {number} sum
* @param {string} val */
function calcStringLength(sum, val) {
if (val === ',' || val === '.') return sum + charPixelWidth * 0.5;
return sum + charPixelWidth;
}
let isBandwidth = $derived(typeof $yScale.bandwidth === 'function');
/** @type {Array<any>} */
let tickVals = $derived(
Array.isArray(ticks)
? ticks
: isBandwidth
? $yScale.domain()
: typeof ticks === 'function'
? ticks($yScale.ticks())
: $yScale.ticks(ticks)
);
let widestTickLen = $derived(
Math.max(
10,
Math.max(...tickVals.map(d => format(d).toString().split('').reduce(calcStringLength, 0)))
)
);
let tickLen = $derived(
tickMarks === true
? labelPosition === 'above'
? (tickMarkLength ?? widestTickLen)
: (tickMarkLength ?? 6)
: 0
);
let x1 = $derived(-tickGutter - (labelPosition === 'above' ? widestTickLen : tickLen));
let y = $derived(isBandwidth ? $yScale.bandwidth() / 2 : 0);
let maxTickValPx = $derived(Math.max(...tickVals.map($yScale)));
</script>
<g class="axis y-axis">
{#each tickVals as tick (tick)}
{@const tickValPx = $yScale(tick)}
<g class="tick tick-{tick}" transform="translate({$xRange[0]}, {tickValPx})">
{#if gridlines === true}
<line class="gridline" {x1} x2={$width} y1={y} y2={y}></line>
{/if}
{#if tickMarks === true}
<line class="tick-mark" {x1} x2={x1 + tickLen} y1={y} y2={y}></line>
{/if}
<text
x={x1}
{y}
dx={dx + (labelPosition === 'even' ? -3 : 0)}
text-anchor={labelPosition === 'above' ? 'start' : 'end'}
dy={dy +
(labelPosition === 'above' || (snapBaselineLabel === true && tickValPx === maxTickValPx)
? -3
: 4)}>{format(tick)}</text
>
</g>
{/each}
</g>
<style>
.tick {
font-size: 11px;
}
.tick line {
stroke: #aaa;
}
.tick .gridline {
stroke-dasharray: 2;
}
.tick text {
fill: #666;
}
.tick.tick-0 line {
stroke-dasharray: 0;
}
</style>
year,value 1979,2 1980,3 1981,5 1982,8 1983,18