jqPlot Show Label for a dashed horizontal line

Question

I want to put a label to the CanvasOverlay Horizontal line and show it in the graph. Haven't found any documentation related to it. But was not successful. Any pointer to fix this issue would be appreciated.

var line3 = [['02/01/2012 00:00:00', '02/01/2012 01:00:00'], ['02/02/2012 00:00:00', '02/01/2012 06:00:00'], ['02/03/2012 00:00:00', '02/01/2012 06:00:00'], ['02/04/2012 00:00:00', '02/01/2012 06:00:00']];
  var plot2 = $.jqplot('chart1', [line3], {
    title:'Mouse Cursor Tracking',
    axes:{
      xaxis:{
          min:'2012-02-01',
      max:'2012-02-10',
      Label: 'Day',
      renderer:$.jqplot.DateAxisRenderer,
          tickOptions:{
            formatString:'%b %#d'
          },
          tickInterval:'1 day'
      },
      yaxis:{
    min:'2012-02-01 00:00:00',
    max:'2012-02-01 24:00:00',
    Label: 'Time',
        renderer:$.jqplot.DateAxisRenderer,
        tickOptions:{
          formatString:'%H'
        },
        tickInterval:'2 hour'
      }
    },
    highlighter: {
      show: false
    },
    cursor: {
      show: true,
      tooltipLocation:'sw'
    },
    canvasOverlay: {
      show: true,
      objects: [
        {horizontalLine: {
          name: 'pebbles',
          y: new $.jsDate( '2012-02-01 05:00:00').getTime(),
          lineWidth: 3,
          color: 'rgb(100, 55, 124)',
          shadow: true,
          lineCap: 'butt',
          xOffset: 0
        }},
        {dashedHorizontalLine: {
          name: 'bam-bam',
          y: new $.jsDate( '2012-02-01 10:00:00').getTime(),
          lineWidth: 4,
          dashPattern: [8, 16],
          lineCap: 'round',
          xOffset: '25',
          color: 'rgb(66, 98, 144)',
          shadow: false
        }}
      ]
    }           
  });

Answer 1

I recently had this same problem and came up with a solution that seems to work pretty well. First of all, you'll need to create a new function so that you can pass in the plot object "plot2". You can then access the various properties of your axes to help calculate where jqplot is rendering your horizontal line.

function applyChartText(plot, text, lineValue) {
     var maxVal = plot.axes.yaxis.max;
     var minVal = plot.axes.yaxis.min;
     var range = maxVal + Math.abs(minVal); // account for negative values  
     var titleHeight = plot.title.getHeight();

     if (plot.title.text.indexOf("<br") > -1) { // account for line breaks in the title
          titleHeight = titleHeight * 0.5; // half it
     } 

     // you now need to calculate how many pixels make up each point in your y-axis
     var pixelsPerPoint = (plot._height - titleHeight  - plot.axes.xaxis.getHeight()) / range;

     var valueHeight = ((maxVal - lineValue) * pixelsPerPoint) + 10;

     // insert the label div as a child of the jqPlot parent
     var title_selector = $(plot.target.selector).children('.jqplot-overlayCanvas-canvas');
     $('<div class="jqplot-point-label " style="position:absolute;  text-align:right;width:95%;top:' + valueHeight + 'px;">' + text + '</div>').insertAfter(title_selector);
}

You're essentially grabbing the size of your graph's div, then subtracting out the # of pixels that make up the graph's title and the text of the x-axis labels. Then you can calculate how many pixels make up each point in your y-axis. Then it's just a matter of seeing where your line fits within the range and applying your label accordingly. You may have to tweak it in a few places, but this should work pretty well.