Chartjs random colors for each part of pie chart with data dynamically from database

Question

I want to set dynamically a color for each part of Pie Chart. Since the chart is dynamically created from database I want for each part that is added to the chart(from database) a different color.

I was trying to do this:

$(document).ready(function() {
$.ajax({
url: "http://localhost/chartjs/projects_chart.php",
method: "GET",
success: function(data) {
    console.log(data);
    var ict_unit = [];
    var efficiency = [];
    var dynamicColors = function() {
        var r = Math.floor(Math.random() * 255);
        var g = Math.floor(Math.random() * 255);
        var b = Math.floor(Math.random() * 255);
        return "rgb(" + r + "," + g + "," + b + ")";
    };

    for (var i in data) {
        ict_unit.push("ICT Unit " + data[i].ict_unit);
        efficiency.push(data[i].efficiency);
         var coloR=dynamicColors();
    }
    var chartData = {

        labels: ict_unit,
        datasets: [{
            label: 'Efficiency ',
            //strokeColor:backGround,

            backgroundColor: [coloR],

            borderColor: 'rgba(200, 200, 200, 0.75)',
            //hoverBackgroundColor: 'rgba(200, 200, 200, 1)',
            hoverBorderColor: 'rgba(200, 200, 200, 1)',
            data: efficiency
        }]
    };

    var ctx = $("#my-canvas");
    var barGraph = new Chart(ctx, {
        type: 'pie',
        data: chartData
    })
},
error: function(data) {

    console.log(data);
   },
  });
 });

But I only get one color for the first part of the pie chart.

Could you help me?

Answer 1

You should create a separate array for colors ( just like the ict_unit and efficiency ) , instead of assigning a random color value each time to the coloR variable.

Here is the revised version of your code :

 $(document).ready(function() { $.ajax({ url: "https://jsonblob.com/api/jsonBlob/a7176bce-84e0-11e7-8b99-016f34757045", method: "GET", success: function(data) { console.log(data); var ict_unit = []; var efficiency = []; var coloR = []; var dynamicColors = function() { var r = Math.floor(Math.random() * 255); var g = Math.floor(Math.random() * 255); var b = Math.floor(Math.random() * 255); return "rgb(" + r + "," + g + "," + b + ")"; }; for (var i in data) { ict_unit.push("ICT Unit " + data[i].ict_unit); efficiency.push(data[i].efficiency); coloR.push(dynamicColors()); } var chartData = { labels: ict_unit, datasets: [{ label: 'Efficiency ', //strokeColor:backGround, backgroundColor: coloR, borderColor: 'rgba(200, 200, 200, 0.75)', //hoverBackgroundColor: 'rgba(200, 200, 200, 1)', hoverBorderColor: 'rgba(200, 200, 200, 1)', data: efficiency }] }; var ctx = $("#my-canvas"); var barGraph = new Chart(ctx, { type: 'pie', data: chartData }) }, error: function(data) { console.log(data); }, }); }); 

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script> <script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.6.0/Chart.min.js"></script> <canvas id="my-canvas"></canvas> 

Answer 2

An example snippet for rgb color picker between 235 and 52

 const randomNum = () => Math.floor(Math.random() * (235 - 52 + 1) + 52); const randomRGB = () => `rgb(${randomNum()}, ${randomNum()}, ${randomNum()})`; console.log(randomRGB());

Resource:

• https://stackoverflow.com/a/45772013/5994546
• https://stackoverflow.com/a/7228322/5994546
• https://www.google.com/search?q=color+picker

Answer 3

Another consideration can be have a Set and avoid color repetition, like this:

let data = []; // Some data
let data_labels = []; // Some data labels
let randomBackgroundColor = [];
let usedColors = new Set();

let dynamicColors = function() {
    let r = Math.floor(Math.random() * 255);
    let g = Math.floor(Math.random() * 255);
    let b = Math.floor(Math.random() * 255);
    let color = "rgb(" + r + "," + g + "," + b + ")";

    if (!usedColors.has(color)) {
        usedColors.add(color);
        return color;
    } else {
        return dynamicColors();
    }
};

for (let i in data) {
    randomBackgroundColor.push(dynamicColors());
}

let pie_config = {
    type: 'pie',
    data: {
        datasets: [{
            data: data,
            backgroundColor: randomBackgroundColor,
            label: 'Label'
        }],
        labels: data_labels
    },
    options: {
        responsive: true
    }
};