How to set x axis value as tooltip in flot charts textual data

Question

I tried with following code in Flot char to draw a chart. Chart is plotting as expected but not tooltip

$(function() {

  var data = [
    ["Aug 06", 2],
    ["Aug 07", 1],
    ["Aug 08", 1.5],
    ["Aug 09", 0],
    ["Aug 10", 0],
    ["Aug 11", 0],
    ["Aug 12", 0]
  ];
  var options = {

    series: {
      lines: {
        show: true,
        lineWidth: 1,
        fill: true,
        fillColor: {
          colors: [{
            opacity: 0.5
          }, {
            opacity: 0.2
          }]
        }
      },
      points: {
        show: true,
        lineWidth: 2
      },
      shadowSize: 0
    },
    grid: {
      hoverable: true,
      clickable: true,
      tickColor: "#eeeeee",
      borderWidth: 0,
      hoverable: true,
      clickable: true
    },
    tooltip: true,
    tooltipOpts: {
      content: "Your sales for <b>%x</b> was <span>$%y</span>",
      defaultTheme: false
    },
    xaxis: {
      mode: "categories",
      tickLength: 0
    },
    yaxis: {
      min: 0
    },
    selection: {
      mode: "x"
    }
  };
  $.plot("#section-chart", [data], options);

  // Add the Flot version string to the footer

  $("#footer").prepend("Flot " + $.plot.version + " &ndash; ");
});

#section-chart {
  width: 600px;
  height: 300px;
}

<link href="http://www.flotcharts.org/flot/examples/examples.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/flot/0.8.3/jquery.flot.min.js"></script>


<script src="https://cdnjs.cloudflare.com/ajax/libs/flot.tooltip/0.9.0/jquery.flot.tooltip.min.js" integrity="sha512-oQJB9y5mlxC4Qp62hdJi/J1NzqiGlpprSfkxVNeosn23mVn5JA4Yn+6f26wWOWCDbV9CxgJzFfVv9DNLPmhxQg==" crossorigin="anonymous"></script>


<div id="section-chart" class="demo-placeholder"></div>

When hover the values, tooltip shows "Your sales for %x was $2" instead it should shows Your sales for Aug 06 was $2 Here how should i pass x axis values as tooltip in flot chart? What i have done wrong on this. kindly advice ?

Answer 1

The solution is using tooltipOpts -> content method with a callback function to properly return dynamic data to the label.

I figured out that passing a 4th argument to the callback function of the "tooltipOpts" actually gives you the whole data object from which the chart/graph is constructed from. From here, you can easily extract the X axis labels, using the second argument of this same function as the index of the label to extract.

EXAMPLE:

Data object I'm passing to the plot function:

[
    {
        data: [[1,47478],[2,24500],[3,40177],[4,10512],[5,10512],[6,10512],[7,43439]],
        points: { show: true, radius: 3},
        splines: { show: true, tension: 0.45, lineWidth: 0, fill: 0.4}
    }
],
{
    colors: ['#0cc2aa'],
    series: { shadowSize: 3 },
    xaxis: {
        show: true,
        font: { color: '#ccc' },
        position: 'bottom',
        ticks: [[1,'Thursday'],[2,'Friday'],[3,'Saturday'],[4,'Sunday'],[5,'Monday'],[6,'Tuesday'],[7,'Wednesday']],
    },
    yaxis:{ show: true, font: { color: '#ccc' }, min:1},
    grid: { hoverable: true, clickable: true, borderWidth: 0, color: 'rgba(120,120,120,0.5)' },
    tooltip: true,
    tooltipOpts: {
        content: function(data, x, y, dataObject) {
            var XdataIndex = dataObject.dataIndex;
            var XdataLabel = dataObject.series.xaxis.ticks[XdataIndex].label;
            return y + ' impressions for all of your posts on ' + XdataLabel;
        },
        defaultTheme: false,
        shifts: { x: 0, y: -40 }
    }
}

Chart rendered from the above data object:

As you can see on the image preview, the logic used to render the label's content dynamically form the actual data is this:

tooltipOpts: {
    content: function(data, x, y, dataObject) {
        var XdataIndex = dataObject.dataIndex;
        var XdataLabel = dataObject.series.xaxis.ticks[XdataIndex].label;
        return y + ' impressions for all of your posts on ' + XdataLabel;
    },
    defaultTheme: false,
    shifts: { x: 0, y: -40 }
}

Answer 2

The easiest way to solve your problem is to replace the content string with a callback:

tooltipOpts : {
        content : getTooltip,
        defaultTheme : false
      },

I defined getTooltip to get your desired output:

function getTooltip(label, x, y) {
    return "Your sales for " + x + " was $" + y; 
}

It works, as you can see in the updated jsFiddle, but you may want to consider the advice of captain, in comments, and see what's best in your case.