Question

I have a figure including two lines (one horizontal line, and one parabolic curve), and I would like to show the value of the crossing over point as well as label it with text “MSY”. I tried to use the option pointLabels, but it seemed like I did not find the right way. Can anyone give me some hints? Here is the demo of the problem.

jquery code:

$(document).ready(function() {
    $.jqplot.config.enablePlugins = true;
    var s1 = [[0.0, 0.0], [1.0, 0.036], [2.0, 0.064], [3.0, 0.084], [4.0, 0.096], [5.0, 0.1], [6.0, 0.096], [7.0, 0.084], [8.0, 0.063], [9.0, 0.036], [10.0, 0.0]];

    $.jqplot('chart1', [s1], {
        seriesDefaults: {
            showMarker: false,
            pointLabels: {
                show: false
            }
        },
        axes: {
            xaxis: {
                label: 'X label',
                pad: 0
            },
            yaxis: {
                label: 'Y label',
                labelRenderer: $.jqplot.CanvasAxisLabelRenderer
            }
        },
        legend: {
            show: true,
            location: 'ne',
            placement: 'inside',
            fontSize: '11px'
        },
        canvasOverlay: {
            show: true,
            objects: [
                {
                horizontalLine: {
                    y: 0.1,
                    color: 'rgb(100, 55, 124)',
                    show: true,
                }}
            ]
        },
        pointLabels: {
            show: true,
            labels: [[5, 0.10]],
            hideZeros: true
        }
    })
})​

Answer 1

There is no straight solution but assuming the parabola to be uniform. I just made some assumptions to calculate the vertex of a parabola. Its just an approximation .And prepared an array that could be feeded to Series label.

var k = Math.round(s1.length / 2); //Assuming your Parabola to be uniform
    var l = [];
    var i=0;
    while(i<(k-1))
    {
    l.push("");
        i++;
    }
    l.push('MSY');

Now we have the l array now I would feed it to the series option so as to get the required result.

 series: [
            {
            pointLabels: {
                show: true,
                labels: l
            }}],

I have made the necessary changes in fiddle and updated it http://jsfiddle.net/JWhmQ/292/ .
I would recommend you to find a small plugin or build a small script which would give you the tip or vertex of the parabola and use the above for that. It would solve your problem.