Chart.LogarithmicLine.js

LogarithmicLine plugin for Chart.js chartjs.org

Usage

Introduction

A line chart with logarithmic y-axis is a way of showing data with a high value range.

Example image

Example usage

var myLogarithmicLineChart = new Chart(ctx).LogarithmicLine(data, options);

Data structure

var data = {
  labels: ["January", "February", "March", "April", "May", "June", "July"],
  datasets: [
  {
    label: "My First dataset",
    fillColor: "rgba(220,220,220,0.5)",
    strokeColor: "rgba(220,220,220,0.8)",
    highlightFill: "rgba(220,220,220,0.75)",
    highlightStroke: "rgba(220,220,220,1)",
    data: [1, 15, 96, 150, 600, 5000, 9000]
  },
  {
    label: "My Second dataset",
    fillColor: "rgba(151,187,205,0.5)",
    strokeColor: "rgba(151,187,205,0.8)",
    highlightFill: "rgba(151,187,205,0.75)",
    highlightStroke: "rgba(151,187,205,1)",
    data: [120, 9, 65, 300, 700, 1200, 900]
  }
  ]
};

Chart Options

These are the customisation options specific to LogarithmicLine charts.

{

  ///Boolean - Whether grid lines are shown across the chart
  scaleShowGridLines : true,

  //String - Colour of the grid lines
  scaleGridLineColor : "rgba(0,0,0,.05)",

  //Number - Width of the grid lines
  scaleGridLineWidth : 1,

  //Boolean - Whether the line is curved between points
  bezierCurve : true,

  //Number - Tension of the bezier curve between points
  bezierCurveTension : 0.4,

  //Boolean - Whether to show a dot for each point
  pointDot : true,

  //Number - Radius of each point dot in pixels
  pointDotRadius : 4,

  //Number - Pixel width of point dot stroke
  pointDotStrokeWidth : 1,

  //Number - amount extra to add to the radius to cater for hit detection outside the drawn point
  pointHitDetectionRadius : 20,

  //Boolean - Whether to show a stroke for datasets
  datasetStroke : true,

  //Number - Pixel width of dataset stroke
  datasetStrokeWidth : 2,

  //Boolean - Whether to fill the dataset with a colour
  datasetFill : true,

  //String - A legend template
  legendTemplate : "<ul class=\"<%=name.toLowerCase()%>-legend\"><% for (var i=0; i<datasets.length; i++){%><li><span style=\"background-color:<%=datasets[i].strokeColor%>\"></span><%if(datasets[i].label){%><%=datasets[i].label%><%}%></li><%}%></ul>"

}

You can override these for your Chart instance by passing a second argument into the LogarithmicLine method as an object with the keys you want to override.

For example, we could have a logarithmic line chart without a stroke on each dataset by doing the following:

new Chart(ctx).LogarithmicLine(data, {
  datasetStroke: false
  });
  // This will create a chart with all of the default options, merged from the global config,
  //  and the LogarithmicLine chart defaults but this particular instance will have `datasetStroke` set to false.

We can also change these defaults values for each LogarithmicLine type that is created, this object is available at Chart.defaults.LogarithmicLine.

Prototype methods

.getPointsAtEvent( event )

Calling getPointsAtEvent(event) on your Chart instance passing an argument of an event, or jQuery event, will return the point elements that are at that the same position of that event.

canvas.onclick = function(evt){
  var activePoints = myLogarithmicLineChart.getPointsAtEvent(evt);
  // => activePoints is an array of points on the canvas that are at the same position as the click event.
};

This functionality may be useful for implementing DOM based tooltips, or triggering custom behaviour in your application.

.update( )

Calling update() on your Chart instance will re-render the chart with any updated values, allowing you to edit the value of multiple existing points, then render those in one animated render loop.

myLogarithmicLineChart.datasets[0].lines[2].value = 50;
// Would update the first dataset's value of 'March' to be 50
myLogarithmicLineChart.update();
// Calling update now animates the position of March from 96 to 50.

.addData( valuesArray, label )

Calling addData(valuesArray, label) on your Chart instance passing an array of values for each dataset, along with a label for those lines.

// The values array passed into addData should be one for each dataset in the chart
myLogarithmicLineChart.addData([40, 60], "August");
// The new data will now animate at the end of the chart.

.removeData( )

Calling removeData() on your Chart instance will remove the first value for all datasets on the chart.

myLogarithmicLineChart.removeData();
// The chart will now animate and remove the first point

License

Chart.LogarithmicLine.js is available under the MIT license.

Bugs & issues

When reporting bugs or issues, if you could include a link to a simple jsbin or similar demonstrating the issue, that'd be really helpful.