How to add an offset to a dataset in Chart js

Question

I was able to add an offset to the X Labels but I would like to add an offset to all the points in the dataset. Is it possible?

This is the code I'm using:

var myChart = new Chart.Line(ctx, {
    type: 'line',
    data: {
        labels: ["JAN", "FEB", "MAR", "APR", "MAY", "JUN", "JUL", "AUG", "SEP", "OCT", "NOV", "DEC", ""],
        datasets: [{
            data: [5, 10.5, 18.2, 33.9, 121.2, 184.9, 179.9, 196.1, 158.3, 166.3, 66.4, 20.6, null],
            pointLabelFontSize : 4,
            borderWidth: 2,
            fill: false,
            lineTension: .3,
            borderColor: "#f37029",
            borderCapStyle: 'round',
            borderDash: [],
            borderDashOffset: 0.0,
            borderJoinStyle: 'bevel',
            pointBorderColor: "#f37029",
            pointBackgroundColor: "#f37029",
            pointBorderWidth: 1,
            pointHoverRadius: 4,
            pointHoverBackgroundColor: "rgba(220,220,220,1)",
            pointHoverBorderColor: "rgba(220,220,220,1)",
            pointHoverBorderWidth: 2,
            pointRadius: 4,
            pointHitRadius: 10,
            spanGaps: false,
        }]
    },
    options: {
        scales: {
            xAxes: [{
                gridLines: {
                    offsetGridLines: true,
                    display: false,
                    borderDash: [6, 2],
                    tickMarkLength:5
                },
                ticks: {
                     fontSize: 8,
                     labelOffset: 10,
                     maxRotation: 0
                }}],
            yAxes: [{
                gridLines: {
                    display:false
                },
                ticks: {
                    beginAtZero: true,
                    max: 200,
                    min: 0,
                    stepSize: 20,
                    fontSize: 8
                }
            }]
        },
        legend: {
            display: false
        },
        responsive: false,
        maintainAspectRatio: true
    }
});

I would like to apply that offset to all the points, in the image I just added an arrow to the JAN/DEC but I would like to apply it to all of them.

I tried adding a null data, the problem is that I don't want to show the first dashed grid.

Any ideas? Thanks in advance.

Answer 1

You can achieve this using Chart.js plugins. They let you handle specific events triggered during the chart creation (beforeInit, afterUpdate, afterDraw ...) and are also easy to implement :

Chart.pluginService.register({
    afterUpdate: function(chart) {
        // This will be triggered after every update of the chart
    }
});

Now you just have to loop through your dataset data model (the property used to draw charts) and add the offset you want :

Chart.pluginService.register({
    afterUpdate: function(chart) {
        // We get the dataset and set the offset here
        var dataset = chart.config.data.datasets[0];
        var offset = 20;

        // For every data in the dataset ...
        for (var i = 0; i < dataset._meta[0].data.length; i++) {
            // We get the model linked to this data
            var model = dataset._meta[0].data[i]._model;

            // And add the offset to the `x` property
            model.x += offset;

            // .. and also to these two properties
            // to make the bezier curve fits the new graph
            model.controlPointNextX += offset;
            model.controlPointPreviousX += offset;
        }
    }
});

You can see your example working on this jsFiddle and here is its result :

Answer 2

Check out - http://www.chartjs.org/docs/latest/axes/cartesian/ .

In chapter "Common Configuration",there is a Boolean attribute offset. Default value is false (except in case of bar chart)

If true, extra space is added to the both edges and the axis is scaled to fit into the chart area. This is set to true in the bar chart by default.

So you can just set it to true, and it should work.