Calling a function of an external Javascript on button click

$(function() {
  $('button').click(function() {
    // Clean up old chart contents
    $("#pieChart").empty();
    // Clean up Tooltips created by chart
    $('.pieTip').remove();
    // Draw a new chart
    $("#pieChart").drawPieChart([{
      title: "Tokyo",
      value: 180,
      color: "#02B3E7"
    }, {
      title: "San Francisco",
      value: 60,
      color: "#CFD3D6"
    }, {
      title: "London",
      value: 50,
      color: "#736D79"
    }, {
      title: "New York",
      value: 30,
      color: "#776068"
    }, {
      title: "Sydney",
      value: 20,
      color: "#EB0D42"
    }, {
      title: "Berlin",
      value: 20,
      color: "#FFEC62"
    }, {
      title: "Osaka",
      value: 7,
      color: "#04374E"
    }]);
  });
});

/*!
 * jquery.drawPieChart.js
 * Version: 0.3(Beta)
 * Inspired by Chart.js(http://www.chartjs.org/)
 *
 * Copyright 2013 hiro
 * https://github.com/githiro/drawPieChart
 * Released under the MIT license.
 */
;
(function($, undefined) {
  $.fn.drawPieChart = function(data, options) {
    var $this = this,
      W = $this.width(),
      H = $this.height(),
      centerX = W / 2,
      centerY = H / 2,
      cos = Math.cos,
      sin = Math.sin,
      PI = Math.PI,
      settings = $.extend({
        segmentShowStroke: true,
        segmentStrokeColor: "#fff",
        segmentStrokeWidth: 1,
        baseColor: "#fff",
        baseOffset: 15,
        edgeOffset: 30, //offset from edge of $this
        pieSegmentGroupClass: "pieSegmentGroup",
        pieSegmentClass: "pieSegment",
        lightPiesOffset: 12, //lighten pie's width
        lightPiesOpacity: .3, //lighten pie's default opacity
        lightPieClass: "lightPie",
        animation: true,
        animationSteps: 90,
        animationEasing: "easeInOutExpo",
        tipOffsetX: -15,
        tipOffsetY: -45,
        tipClass: "pieTip",
        beforeDraw: function() {},
        afterDrawed: function() {},
        onPieMouseenter: function(e, data) {},
        onPieMouseleave: function(e, data) {},
        onPieClick: function(e, data) {}
      }, options),
      animationOptions = {
        linear: function(t) {
          return t;
        },
        easeInOutExpo: function(t) {
          var v = t < .5 ? 8 * t * t * t * t : 1 - 8 * (--t) * t * t * t;
          return (v > 1) ? 1 : v;
        }
      },
      requestAnimFrame = function() {
        return window.requestAnimationFrame ||
          window.webkitRequestAnimationFrame ||
          window.mozRequestAnimationFrame ||
          window.oRequestAnimationFrame ||
          window.msRequestAnimationFrame ||
          function(callback) {
            window.setTimeout(callback, 1000 / 60);
          };
      }();

    var $wrapper = $('<svg width="' + W + '" height="' + H + '" viewBox="0 0 ' + W + ' ' + H + '" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"></svg>').appendTo($this);
    var $groups = [],
      $pies = [],
      $lightPies = [],
      easingFunction = animationOptions[settings.animationEasing],
      pieRadius = Min([H / 2, W / 2]) - settings.edgeOffset,
      segmentTotal = 0;

    //Draw base circle
    var drawBasePie = function() {
      var base = document.createElementNS('http://www.w3.org/2000/svg', 'circle');
      var $base = $(base).appendTo($wrapper);
      base.setAttribute("cx", centerX);
      base.setAttribute("cy", centerY);
      base.setAttribute("r", pieRadius + settings.baseOffset);
      base.setAttribute("fill", settings.baseColor);
    }();

    //Set up pie segments wrapper
    var pathGroup = document.createElementNS('http://www.w3.org/2000/svg', 'g');
    var $pathGroup = $(pathGroup).appendTo($wrapper);
    $pathGroup[0].setAttribute("opacity", 0);

    //Set up tooltip
    var $tip = $('<div class="' + settings.tipClass + '" />').appendTo('body').hide(),
      tipW = $tip.width(),
      tipH = $tip.height();

    for (var i = 0, len = data.length; i < len; i++) {
      segmentTotal += data[i].value;
      var g = document.createElementNS('http://www.w3.org/2000/svg', 'g');
      g.setAttribute("data-order", i);
      g.setAttribute("class", settings.pieSegmentGroupClass);
      $groups[i] = $(g).appendTo($pathGroup);
      $groups[i]
        .on("mouseenter", pathMouseEnter)
        .on("mouseleave", pathMouseLeave)
        .on("mousemove", pathMouseMove)
        .on("click", pathClick);

      var p = document.createElementNS('http://www.w3.org/2000/svg', 'path');
      p.setAttribute("stroke-width", settings.segmentStrokeWidth);
      p.setAttribute("stroke", settings.segmentStrokeColor);
      p.setAttribute("stroke-miterlimit", 2);
      p.setAttribute("fill", data[i].color);
      p.setAttribute("class", settings.pieSegmentClass);
      $pies[i] = $(p).appendTo($groups[i]);

      var lp = document.createElementNS('http://www.w3.org/2000/svg', 'path');
      lp.setAttribute("stroke-width", settings.segmentStrokeWidth);
      lp.setAttribute("stroke", settings.segmentStrokeColor);
      lp.setAttribute("stroke-miterlimit", 2);
      lp.setAttribute("fill", data[i].color);
      lp.setAttribute("opacity", settings.lightPiesOpacity);
      lp.setAttribute("class", settings.lightPieClass);
      $lightPies[i] = $(lp).appendTo($groups[i]);
    }

    settings.beforeDraw.call($this);
    //Animation start
    triggerAnimation();

    function pathMouseEnter(e) {
      var index = $(this).data().order;
      $tip.text(data[index].title + ": " + data[index].value).fadeIn(200);
      if ($groups[index][0].getAttribute("data-active") !== "active") {
        $lightPies[index].animate({
          opacity: .8
        }, 180);
      }
      settings.onPieMouseenter.apply($(this), [e, data]);
    }

    function pathMouseLeave(e) {
      var index = $(this).data().order;
      $tip.hide();
      if ($groups[index][0].getAttribute("data-active") !== "active") {
        $lightPies[index].animate({
          opacity: settings.lightPiesOpacity
        }, 100);
      }
      settings.onPieMouseleave.apply($(this), [e, data]);
    }

    function pathMouseMove(e) {
      $tip.css({
        top: e.pageY + settings.tipOffsetY,
        left: e.pageX - $tip.width() / 2 + settings.tipOffsetX
      });
    }

    function pathClick(e) {
      var index = $(this).data().order;
      var targetGroup = $groups[index][0];
      for (var i = 0, len = data.length; i < len; i++) {
        if (i === index) continue;
        $groups[i][0].setAttribute("data-active", "");
        $lightPies[i].css({
          opacity: settings.lightPiesOpacity
        });
      }
      if (targetGroup.getAttribute("data-active") === "active") {
        targetGroup.setAttribute("data-active", "");
        $lightPies[index].css({
          opacity: .8
        });
      } else {
        targetGroup.setAttribute("data-active", "active");
        $lightPies[index].css({
          opacity: 1
        });
      }
      settings.onPieClick.apply($(this), [e, data]);
    }

    function drawPieSegments(animationDecimal) {
      var startRadius = -PI / 2, //-90 degree
        rotateAnimation = 1;
      if (settings.animation) {
        rotateAnimation = animationDecimal; //count up between0~1
      }

      $pathGroup[0].setAttribute("opacity", animationDecimal);

      //draw each path
      for (var i = 0, len = data.length; i < len; i++) {
        var segmentAngle = rotateAnimation * ((data[i].value / segmentTotal) * (PI * 2)), //start radian
          endRadius = startRadius + segmentAngle,
          largeArc = ((endRadius - startRadius) % (PI * 2)) > PI ? 1 : 0,
          startX = centerX + cos(startRadius) * pieRadius,
          startY = centerY + sin(startRadius) * pieRadius,
          endX = centerX + cos(endRadius) * pieRadius,
          endY = centerY + sin(endRadius) * pieRadius,
          startX2 = centerX + cos(startRadius) * (pieRadius + settings.lightPiesOffset),
          startY2 = centerY + sin(startRadius) * (pieRadius + settings.lightPiesOffset),
          endX2 = centerX + cos(endRadius) * (pieRadius + settings.lightPiesOffset),
          endY2 = centerY + sin(endRadius) * (pieRadius + settings.lightPiesOffset);
        var cmd = [
          'M', startX, startY, //Move pointer
          'A', pieRadius, pieRadius, 0, largeArc, 1, endX, endY, //Draw outer arc path
          'L', centerX, centerY, //Draw line to the center.
          'Z' //Cloth path
        ];
        var cmd2 = [
          'M', startX2, startY2,
          'A', pieRadius + settings.lightPiesOffset, pieRadius + settings.lightPiesOffset, 0, largeArc, 1, endX2, endY2, //Draw outer arc path
          'L', centerX, centerY,
          'Z'
        ];
        $pies[i][0].setAttribute("d", cmd.join(' '));
        $lightPies[i][0].setAttribute("d", cmd2.join(' '));
        startRadius += segmentAngle;
      }
    }

    var animFrameAmount = (settings.animation) ? 1 / settings.animationSteps : 1, //if settings.animationSteps is 10, animFrameAmount is 0.1
      animCount = (settings.animation) ? 0 : 1;

    function triggerAnimation() {
      if (settings.animation) {
        requestAnimFrame(animationLoop);
      } else {
        drawPieSegments(1);
      }
    }

    function animationLoop() {
      animCount += animFrameAmount; //animCount start from 0, after "settings.animationSteps"-times executed, animCount reaches 1.
      drawPieSegments(easingFunction(animCount));
      if (animCount < 1) {
        requestAnimFrame(arguments.callee);
      } else {
        settings.afterDrawed.call($this);
      }
    }

    function Max(arr) {
      return Math.max.apply(null, arr);
    }

    function Min(arr) {
      return Math.min.apply(null, arr);
    }
    return $this;
  };
})(jQuery);

.chart {
  position: absolute;
  width: 250px;
  height: 250px;
  top: 100%;
  left: 50%;
  margin: -225px 0 0 -225px;
}
.pieTip {
  position: absolute;
  float: left;
  min-width: 30px;
  max-width: 300px;
  padding: 5px 18px 6px;
  border-radius: 2px;
  background: rgba(255, 255, 255, .97);
  color: #444;
  font-size: 19px;
  text-shadow: 0 1px 0 #fff;
  text-transform: uppercase;
  text-align: center;
  line-height: 1.3;
  letter-spacing: .06em;
  box-shadow: 0 0 3px rgba(0, 0, 0, 0.2), 0 1px 2px rgba(0, 0, 0, 0.5);
  -webkit-transform: all .3s;
  -moz-transform: all .3s;
  -ms-transform: all .3s;
  -o-transform: all .3s;
  transform: all .3s;
  pointer-events: none;
}
.pieTip:after {
  position: absolute;
  left: 50%;
  bottom: -6px;
  content: "";
  height: 0;
  margin: 0 0 0 -6px;
  border-right: 5px solid transparent;
  border-left: 5px solid transparent;
  border-top: 6px solid rgba(255, 255, 255, .95);
  line-height: 0;
}
.chart path {
  cursor: pointer;
}

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="pieChart" class="chart"></div>
<button>Animate</button>