d3.js Bar chart supporting negative values

Question

I am using d3.js and angular js directive for creating bar graph in our application. The code I have used is given below . This works for positive values.But it is not displayed for negative values.What chages I have to apply for supporting negative values.

Html page for graph

<cr-d3-bars data='myData'></cr-d3-bars>

Js file for graph

   mainApp.directive('crD3Bars', function() {
return {
restrict: 'E',
scope: {
  data: '='
},
link: function (scope, element) {
    var margin = {top: 20, right: 20, bottom: 30, left: 40},
    width = 480 - margin.left - margin.right,
    height = 360 - margin.top - margin.bottom;
  var svg = d3.select(element[0])
    .append("svg")
    .attr('width', width + margin.left + margin.right)
    .attr('height', height + margin.top + margin.bottom)
    .append("g")
      .attr("transform", "translate(" + margin.left + "," + margin.top + ")");

  var x = d3.scale.ordinal().rangeRoundBands([0, width], .1);
  var y = d3.scale.linear().range([height, 0]);

  var xAxis = d3.svg.axis()
      .scale(x)
      .orient("bottom");

  var yAxis = d3.svg.axis()
      .scale(y)
      .orient("left")
      .ticks(10);

  //Render graph based on 'data'
  scope.render = function(data) {
    //Set our scale's domains
    x.domain(data.map(function(d) { return d.name; }));
    y.domain([0, d3.max(data, function(d) { return d.count; })]);

    //Redraw the axes
    svg.selectAll('g.axis').remove();
    //X axis
    svg.append("g")
        .attr("class", "x axis")
        .attr("transform", "translate(0," + height + ")")
        .call(xAxis);

    //Y axis
    svg.append("g")
        .attr("class", "y axis")
        .call(yAxis)
      .append("text")
        .attr("transform", "rotate(-90)")
        .attr("y", 6)
        .attr("dy", ".71em")
        .style("text-anchor", "end")
        .text("Count");

    var bars = svg.selectAll(".bar").data(data);
    bars.enter()
      .append("rect")
      .attr("class", "bar")
      .attr("x", function(d) { return x(d.name); })
      .attr("width", x.rangeBand());

    //Animate bars
    bars
        .transition()
        .duration(1000)
        .attr('height', function(d) { return height - y(d.count); })
        .attr("y", function(d) { return y(d.count); });
  };

I am supplying data as shown below

$scope.myData = [
                            {name: 'AngularJS', count: 300},
                            {name: 'D3.JS', count: 150},
                            {name: 'jQuery', count:10000},
                            {name: 'Backbone.js', count: 300},
                            {name: 'Ember.js', count: 100},
                           {name: 'hi.js', count: 300},
                            {name: 'hl.js', count: -100}
                        ];

Any one have solution please share with me

Answer 1

First you have to change the y domain to accept negative values:

y.domain([d3.min(data,function(d){return d.count}), d3.max(data, function(d) { return d.count; })]);

Then you have to play with the y and height attributes of bars to make sure that the boxes are located at the correct place:

.attr("y", function(d) { return y(Math.max(0, d.count)); })
.attr("height", function(d) { return Math.abs(y(d.count) - y(0)); })

Here is a working example (used in another answer): http://jsfiddle.net/chrisJamesC/tNdJj/4/