Rendering issue in d3.js bar graph - angularjs

Question

I am developing d3.js bar graph integrating with angular Js . The code is given below.
mainApp.directive('ngTest', function() {
return {
restrict: 'AE',
scope: {
data: '='
},
link: function (scope, element) {
var margin = {top: 20, right: 30, bottom: 30, left: 60},
width = 410 - margin.left - margin.right,
height = 230 - margin.top - margin.bottom;
var chart = 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 tip = d3.tip()
.attr('class', 'd3-tip')
.offset([-10, 0])
.html(function(d) {
return "<strong>Frequency:</strong> <span style='color:red'>" + d.value + "</span>";
});
chart.call(tip);
//Render graph based on 'data'
scope.render = function(data) {
var y = d3.scale.linear()
.range([height, 0])
.domain(d3.extent(data, function(d) { return d.value; }))
.nice();
var xAxis = d3.svg.axis().scale(x).orient("bottom");
var yAxis = d3.svg.axis().scale(y).orient("left");
x.domain(data.map(function(d) { return d.name; }));
//Redraw the axes
chart.selectAll('g.axis').remove();
chart.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + (height) + ")")
.call(xAxis)
.selectAll("text")
.style("text-anchor", "end")
.attr("dx", "-.8em")
.attr("dy", ".15em")
.attr("transform", function(d) {
return "rotate(-20)";
});
chart.append("g")
.attr("class", "y axis")
.call(yAxis)
.append("text")
.attr("transform", "rotate(-90)")
.attr("y", 0-margin.left)
.attr("x",0-(height / 2))
.attr("dy", "1em")
.style("text-anchor", "middle")
.text("Value");
chart.selectAll(".bar")
.data(data)
.enter().append("rect")
.attr("class", function(d) { return d.value < 0 ? "bar negative" : "bar positive"; })
.attr("x", function(d) { return x(d.name); })
.attr("y", height)
.attr("height", 0)
.on('mouseover', tip.show)
.on('mouseout', tip.hide)
.transition().duration(2000)
.attr("y", function(d) {return y(Math.max(0, d.value)); })
.attr("height", function(d) {return Math.abs(y(d.value) - y(0)); })
// .attr("width", x.rangeBand());
.attr("width", Math.min.apply(null, [x.rangeBand()-2, 100]));
};
scope.$watch('data', function() {
scope.render(scope.data);
}, true);
}
};
});
The full application is uploaded in fiddle in following address
http://jsfiddle.net/HB7LU/9060/
I have 3 data sets that are given below.
$scope.myData = [
{name: "01-12-2014", value: 4984.6},
{name: "02-12-2014", value: -109.45},
{name: "03-12-2014", value: 474},
{name: "04-12-2014", value: 391.07},
{name: "05-12-2014", value: 106.82},
{name: "06-12-2014", value: -5},
{name: "07-12-2014", value: 30},
{name: "08-12-2014", value: 9}
];
$scope.myData = [
{name: "01-12-2014", value: 474},
{name: "02-12-2014", value: 391.07},
{name: "03-12-2014", value: 106.82},
{name: "08-12-2014", value: 9}
]
The graph is behave normally when applying above data sets.
But the graph behave ubnormally for following dataset which include additional one raw less than 2nd last dataset
$scope.myData2 = [
{name: "01-12-2014", value: 474},
{name: "02-12-2014", value: 391.07},
{name: "03-12-2014", value: 106.82}
];
Since I am new to d3.js I cannot identify the exact problem. If any one know please help me

Answer 1

Your issue stems from how you determine the height of the bars:
.attr("height", function(d) {return Math.abs(y(d.value) - y(0)); })
Here you are setting the height as the difference between the y-value of the data point and the y-value at 0. However, your y-scale starts at the minimum value in your dataset:
var y = d3.scale.linear()
.range([height, 0])
.domain(d3.extent(data, function(d) { return d.value; }))
.nice();
As a result, y(0) can at times be negative. You just didn't notice it with the other two datasets because their minimum values are close to 0. Here's how I would set the height:
.attr("height", function(d) {return Math.abs(y(d.value) - y(d3.min(y.domain()))) })
See updated fiddle and plot below.