Plotfast

Canvas plotting library focused on performance.

Check it out with a million points here!

Usage

npm install plotfast or yarn add plotfast

Or include the plotfast.min.js script and it'll expose the Plotfast global.

Then, in your HTML:

<div id="container"></div>

And initialize the plot in JS:

// Plot will be inserted into this div,
// canvas creation handled automatically
var container = document.getElementById('container');

// Create the plot
var plot = new Plotfast(container);

// Generate 10k points of data
var data = plot.generateData(10000);

// Add the data to the plot
plot.addDataset(data);

// Start rendering the plot
plot.start();

Or use the React component (in beta):

import { Plot } from 'plotfast/react';

const data = generateMyData();

const MyPlot = () => (
    <Plot
        options={{ logging: true }}
        datasets={{ data, options: { type: 'line' } }}
    />
);

Features

Data

Data is an array of objects in the form { x, y }. Data will be sorted by x value on initialization.

// Add new data, with options
plot.addDataset(myData, {
    name: 'My Dataset',
    color: 'red',
});

// Replace the data of an existing dataset
// (Useful for server-side decimation)
plot.updateDataset(0, updatedData);

// Remove a dataset, by index
plot.removeDataset(0);

// Or by name
plot.removeDataset('My Dataset');

// Or remove all datasets
plot.removeDataset();

Plot Options

var plot = new Plotfast(container, {
    logging: true,

    // Dimensions of the canvas
    width: 640,
    height: 480,

    // Labels to display on the axes
    xLabel: 'X axis',
    yLabel: 'Y axis',

    // Colors
    lineColor: 'lightgrey',
    textColor: 'black',
    backgroundColor: 'none',

    // Downsample data to improve performance
    downsample: true,
});

Data Options

var data = [{ x: 1, y: 0 }, { x: 2, y: 5 }];

plot.addDataset(data, {
    name: 'Dataset',
    color: 'black',

    // Will match the plot's downsample setting by default
    downsample: true,
});

Events

// Fires whenever the view changes and gives the new
// min/max for x and y.
plot.addEventListener('viewMoved', event => {
    console.log(event.x1, event.x2, event.y1, event.y2);
});

Development

1. Clone repo, run yarn install
2. Start the development server with yarn start
3. Create a production build with yarn build

Future Plans

• Flesh out plot customization/types
• In Plot React component, all normal Plotfast functionality should be exposed
• Try using WebAssembly to speed up plot downsampling/rendering

Credit

Default downsampling algorithm provided by Sveinn Steinarsson's Largest Triangle Three Buckets Algorithm.

Icons are from Google's Material Icons.