Chart.js - draw horizontal line

Question

I would like to draw a horizontal line in a chart using Chart.js. But I\'m not able to do it.

I\'ve read this question - Chart.js — drawing an arbitrary vertical lin

Answer 1

If you need many lines with certain Y value, try this code

var data = {
    labels: ["JAN", "FEB", "MAR", "APR", "MAY", "JUN", "JUL", "AUG", "SEP", "OCT", "NOV", "DEC"],
    datasets: [{
        data: [12, 3, 2, 1, 8, 8, 2, 2, 3, 5, 7, 1]
    }]
};

var ctx = document.getElementById("LineWithLine").getContext("2d");

Chart.types.Line.extend({
    name: "LineWithLine",
    draw: function () {
        Chart.types.Line.prototype.draw.apply(this, arguments);

        var lines = this.options.limitLines;

        for (var i = lines.length; --i >= 0;) {

            var xStart = Math.round(this.scale.xScalePaddingLeft);
            var linePositionY = this.scale.calculateY(lines[i].value);

            this.chart.ctx.fillStyle = lines[i].color ? lines[i].color : this.scale.textColor;
            this.chart.ctx.font = this.scale.font;
            this.chart.ctx.textAlign = "left";
            this.chart.ctx.textBaseline = "top";

            if (this.scale.showLabels && lines[i].label) {
                this.chart.ctx.fillText(lines[i].label, xStart + 5, linePositionY);
            }

            this.chart.ctx.lineWidth = this.scale.gridLineWidth;
            this.chart.ctx.strokeStyle = lines[i].color ? lines[i].color : this.scale.gridLineColor;

            if (this.scale.showHorizontalLines) {
                this.chart.ctx.beginPath();
                this.chart.ctx.moveTo(xStart, linePositionY);
                this.chart.ctx.lineTo(this.scale.width, linePositionY);
                this.chart.ctx.stroke();
                this.chart.ctx.closePath();
            }

            this.chart.ctx.lineWidth = this.lineWidth;
            this.chart.ctx.strokeStyle = this.lineColor;
            this.chart.ctx.beginPath();
            this.chart.ctx.moveTo(xStart - 5, linePositionY);
            this.chart.ctx.lineTo(xStart, linePositionY);
            this.chart.ctx.stroke();
            this.chart.ctx.closePath();
        }
    }
});

new Chart(ctx).LineWithLine(data, {
    datasetFill : false,
    limitLines: [
        {
            label: 'max',
            value: 17,
            color: 'rgba(255, 0, 0, .8)'
        },
        {
            label: 'min',
            value: 1
        },
        {
            value: 7,
            color: 'rgba(0, 255, 255, .8)'
        }
    ],
});

http://jsfiddle.net/vsh6tcfd/3/