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    2.0.4 • Public • Published

    Signal Processing

    The Signal Processing Plots module is designed for plotting computed signals.


    npm install @signalprocessing/plots --save


    @signalprocessing/windows module can be both imported as commonJS or ES module.

    1. Create index.js

    let fft = require("@signalprocessing/transforms").fft ;
    let amplitudeSpectrum = require("@signalprocessing/plots").amplitudeSpectrum ;
    //Sampling Rate
    let Fs = 1500;
    //Sampling Period
    let T = 1 / Fs;
    //Length of signal
    let L = 1000;
    //Time array
    let t = Array.from({ length: L }, (x, i) => i * T);
    //A signal containing a 30 Hz sinusoid of amplitude 0.5 and a 100 Hz sinusoid of amplitude 1.
    let S = Array.from( t, (x, i) => 0.5 * Math.sin(2 * Math.PI * 30 * x) + Math.sin(2 * Math.PI * 100 * x));
    //Compute the Fourier transform of the signal.
    let [real, imag] = fft(S);
    //Plot amplitude spectrum
    amplitudeSpectrum(real, imag, Fs, "myDiv");
    //myDiv is id of html div element to create plot chart on it.
    1. Create index.html and add index.js as script into your html file. Then create div element with id myDiv
    <html lang="en">
        <meta charset="UTF-8" />
        <meta name="viewport" content="width=device-width, initial-scale=1.0" />
        <div id="myDiv">
          <!-- Plotly chart will be drawn inside this DIV -->
        <script src="./index.js" charset="utf-8"></script>
    1. In Node, there is no browser window. So you should create a web server to serve your html file.
    • To simplify this step I am using Parcel and cross-env modules.

      If you have already setup your http server, then you may skip these step.

      However, I am strongly recommending you to use cross-env and Parcel to make your code works on different platforms.

    • Install and save these modules as development.

    npm install --save-dev cross-env  parcel-bundler
    1. Run the script below in the terminal to see results in the browser. In the first run, it will take a few minutes to build your files.
    cross-env NODE_ENV=development parcel index.html --no-hmr --open
    • Alternatively, you may also add scripts declaration into your package.json file
      "scripts": {
        "watch": "cross-env NODE_ENV=development parcel index.html --no-hmr --open  "
    • And then run the command below in working directory.
    npm run watch

    Amplitude Spectrum




    npm i @signalprocessing/plots

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