Delcon Delcon - 2 months ago 30
Javascript Question

Chart Js Change Label orientation on x-Axis for Line Charts

I am useing chart.js

Similar to this Question I would like to rotate my x-axis labels 90 degrees.
Currently my labels are rotated about 80 degrees with default settings.

enter image description here

Could somebody help me adapt the bar-chart solution for rotating labels so that I can use it on line-charts?

Answer

Using the same method as in the previous answer the only thing that needs to changed is the extension of the graph type. This time it is extending the line chart and the set-up is a little different as the Line charts scale is created in the build scale so this time it is buildScale is overridden so that the custom scale is used and the new option overrideRotation can be passed in. initialize is also overridden but only so that the super initialize can be called and get the ball rolling on building the graph.

var helpers = Chart.helpers;
Chart.MyScale = Chart.Scale.extend({
  calculateXLabelRotation: function() {
    //Get the width of each grid by calculating the difference
    //between x offsets between 0 and 1.

    this.ctx.font = this.font;

    var firstWidth = this.ctx.measureText(this.xLabels[0]).width,
      lastWidth = this.ctx.measureText(this.xLabels[this.xLabels.length - 1]).width,
      firstRotated,
      lastRotated;


    this.xScalePaddingRight = lastWidth / 2 + 3;
    this.xScalePaddingLeft = (firstWidth / 2 > this.yLabelWidth + 10) ? firstWidth / 2 : this.yLabelWidth + 10;

    this.xLabelRotation = 0;
    if (this.display) {
      var originalLabelWidth = helpers.longestText(this.ctx, this.font, this.xLabels),
        cosRotation,
        firstRotatedWidth;
      this.xLabelWidth = originalLabelWidth;
      //Allow 3 pixels x2 padding either side for label readability
      var xGridWidth = Math.floor(this.calculateX(1) - this.calculateX(0)) - 6;

      if (this.overrideRotation) {
        this.xLabelRotation = this.overrideRotation;
        cosRotation = Math.cos(helpers.radians(this.xLabelRotation));
        // We're right aligning the text now.
        if (firstRotated + this.fontSize / 2 > this.yLabelWidth + 8) {
          this.xScalePaddingLeft = firstRotated + this.fontSize / 2;
        }
        this.xScalePaddingRight = this.fontSize / 2;
        this.xLabelWidth = cosRotation * originalLabelWidth;
      } else {
        //Max label rotate should be 90 - also act as a loop counter
        while ((this.xLabelWidth > xGridWidth && this.xLabelRotation === 0) || (this.xLabelWidth > xGridWidth && this.xLabelRotation <= 90 && this.xLabelRotation > 0)) {
          cosRotation = Math.cos(helpers.radians(this.xLabelRotation));

          firstRotated = cosRotation * firstWidth;
          lastRotated = cosRotation * lastWidth;

          // We're right aligning the text now.
          if (firstRotated + this.fontSize / 2 > this.yLabelWidth + 8) {
            this.xScalePaddingLeft = firstRotated + this.fontSize / 2;
          }
          this.xScalePaddingRight = this.fontSize / 2;


          this.xLabelRotation++;
          this.xLabelWidth = cosRotation * originalLabelWidth;

        }
      }
      if (this.xLabelRotation > 0) {
        this.endPoint -= Math.sin(helpers.radians(this.xLabelRotation)) * originalLabelWidth + 3;
      }
    } else {
      this.xLabelWidth = 0;
      this.xScalePaddingRight = this.padding;
      this.xScalePaddingLeft = this.padding;
    }

  },

});

Chart.types.Line.extend({
  name: "MyLine",
  initialize: function(data) {
    Chart.types.Line.prototype.initialize.apply(this, arguments);
  },

  buildScale: function(labels) {
    var self = this;

    var dataTotal = function() {
      var values = [];
      self.eachPoints(function(point) {
        values.push(point.value);
      });

      return values;
    };

    var scaleOptions = {
      templateString: this.options.scaleLabel,
      height: this.chart.height,
      width: this.chart.width,
      ctx: this.chart.ctx,
      textColor: this.options.scaleFontColor,
      offsetGridLines: this.options.offsetGridLines,
      fontSize: this.options.scaleFontSize,
      fontStyle: this.options.scaleFontStyle,
      fontFamily: this.options.scaleFontFamily,
      valuesCount: labels.length,
      beginAtZero: this.options.scaleBeginAtZero,
      integersOnly: this.options.scaleIntegersOnly,
      calculateYRange: function(currentHeight) {
        var updatedRanges = helpers.calculateScaleRange(
          dataTotal(),
          currentHeight,
          this.fontSize,
          this.beginAtZero,
          this.integersOnly
        );
        helpers.extend(this, updatedRanges);
      },
      xLabels: labels,
      font: helpers.fontString(this.options.scaleFontSize, this.options.scaleFontStyle, this.options.scaleFontFamily),
      lineWidth: this.options.scaleLineWidth,
      lineColor: this.options.scaleLineColor,
      showHorizontalLines: this.options.scaleShowHorizontalLines,
      showVerticalLines: this.options.scaleShowVerticalLines,
      gridLineWidth: (this.options.scaleShowGridLines) ? this.options.scaleGridLineWidth : 0,
      gridLineColor: (this.options.scaleShowGridLines) ? this.options.scaleGridLineColor : "rgba(0,0,0,0)",
      padding: (this.options.showScale) ? 0 : this.options.pointDotRadius + this.options.pointDotStrokeWidth,
      showLabels: this.options.scaleShowLabels,
      display: this.options.showScale,
      overrideRotation: this.options.overrideRotation,
    };

    if (this.options.scaleOverride) {
      helpers.extend(scaleOptions, {
        calculateYRange: helpers.noop,
        steps: this.options.scaleSteps,
        stepValue: this.options.scaleStepWidth,
        min: this.options.scaleStartValue,
        max: this.options.scaleStartValue + (this.options.scaleSteps * this.options.scaleStepWidth)
      });
    }


    this.scale = new Chart.MyScale(scaleOptions);
  },
});



var randomScalingFactor = function() {
  return Math.round(Math.random() * 100)
};

var barChartData = {
  labels: ["January", "February", "March", "April", "May", "June", "July"],
  datasets: [{
    fillColor: "rgba(20,20,220,0.2)",
    strokeColor: "rgba(20,20,220,1)",
    pointColor: "rgba(20,20,220,1)",
    pointStrokeColor: "#fff",
    pointHighlightFill: "#fff",
    pointHighlightStroke: "rgba(20,20,220,1)",
    data: [randomScalingFactor(), randomScalingFactor(), randomScalingFactor(), randomScalingFactor(), randomScalingFactor(), randomScalingFactor(), randomScalingFactor()]
  }, {
    fillColor: "rgba(120,120,120,0.2)",
    strokeColor: "rgba(120,220,120,1)",
    pointColor: "rgba(120,120,120,1)",
    pointStrokeColor: "#fff",
    pointHighlightFill: "#fff",
    pointHighlightStroke: "rgba(120,120,120,1)",
    data: [randomScalingFactor(), randomScalingFactor(), randomScalingFactor(), randomScalingFactor(), randomScalingFactor(), randomScalingFactor(), randomScalingFactor()]
  }, {
    fillColor: "rgba(220,220,220,0.2)",
    strokeColor: "rgba(220,220,220,1)",
    pointColor: "rgba(220,220,220,1)",
    pointStrokeColor: "#fff",
    pointHighlightFill: "#fff",
    pointHighlightStroke: "rgba(220,220,220,1)",
    data: [randomScalingFactor(), randomScalingFactor(), randomScalingFactor(), randomScalingFactor(), randomScalingFactor(), randomScalingFactor(), randomScalingFactor()]
  }]

}
window.onload = function() {
  var ctx = document.getElementById("canvas").getContext("2d");
  window.myBar = new Chart(ctx).MyLine(barChartData, {
    overrideRotation: 90
  });
}
<script src="http://www.chartjs.org/assets/Chart.min.js"></script>

<canvas id="canvas" height="150" width="300"></canvas>