Vega-Lite with Streaming Data Updates / Vega

Data Visualization Languages & Tools

Published

Edited

Mar 25, 2021

15 stars

viewof view = vl.markBar()

.data(vl.data().name('data')) // empty data set, provide name for later reference

.encode(

vl.x().fieldO('x').axis({labelAngle: 0}),

vl.y().fieldQ('y').scale({domain: [0, 100]}) // stable y-axis across data draws

)

.render()

// create a button that changes the data when clicked

viewof button = {

const button = html`<button>Update Data</button>`;

button.addEventListener('click', () => {

const add = [];

for (let i = 1; i <= 10; ++i) { // generate random data

add.push({x: i, y: 5 + Math.round(90 * Math.random())});

}

update(view, 'data', add, () => true); // insert new data, remove old data

});

return button;

}

// insert and/or remove tuples using a Vega ChangeSet

// re-run and return (a promise for) the View

function update(view, name, insert, remove) {

const cs = vl.vega.changeset();

if (remove != null) cs.remove(remove);

if (insert != null) cs.insert(insert);

return view.change(name, cs).runAsync();

}

import {vl} from '@vega/vega-lite-api-v5'

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