How to add space between axis and line in D3 line chart? - d3.js

Question

Given this simple chart I created:
var data = [["2013-01-24 06:38:02.235191", 52], ["2013-01-23 06:38:02.235310", 54], ["2013-01-22 06:38:02.235330", 45], ["2013-01-21 06:38:02.235346", 53]],
maxValue = d3.max(data, function (d) { return d[1]; }),
margin = {top: 20, right: 20, bottom: 50, left: 50},
width = 500 - margin.left - margin.right,
height = 300 - margin.top - margin.bottom,
svg, x, y, xAxis, yAxis, line;
$.each(data, function(index, val) {
val[0] = new Date(val[0]);
});
x = d3.time.scale()
.range([0, width])
y = d3.scale.linear()
.domain([0, maxValue])
.range([height, 0]);
xAxis = d3.svg.axis()
.scale(x)
.tickSize(4, 2, 0)
.ticks(d3.time.days, 1)
.tickFormat(d3.time.format("%m/%d"))
.orient("bottom");
yAxis = d3.svg.axis()
.scale(y)
// .ticks(5)
// .tickValues([0, maxValue * 0.25, maxValue * 0.5, maxValue * 0.75, maxValue])
.tickSize(4, 2, 0)
.orient("left");
line = d3.svg.line()
.x(function(d) { return x(d[0]); })
.y(function(d) { return y(d[1]); });
svg = d3.select("#chart-holder").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 + ")");
x.domain(d3.extent(data, function(d) { return d[0]; }));
y.domain(d3.extent(data, function(d) { return d[1]; }));
svg.append("g")
.attr("class", "x axis")
.attr("transform", "translate(0," + height + ")")
.call(xAxis)
.selectAll("text")
.attr("transform", function(d) {
return "rotate(-60)translate(" + -this.getBBox().height * 1.7 + "," +
-this.getBBox().width/4 + ")";
});
svg.append("g")
.attr("class", "y axis")
.call(yAxis);
svg.append("path")
.datum(data)
.attr("class", "line")
.attr("d", line);
svg
.selectAll("circle")
.data(data)
.enter().append("circle")
.attr("fill", "#0b8da0")
.attr("r", 3.5)
.attr("cx", function(d) { return x(d[0]); })
.attr("cy", function(d) { return y(d[1]); });
How can I add a space between axis and line, so it won't touch the axis.
Also is there a way to force yAxis ticks to always start from 0, no matter what is the smallest value in the data set?
Working example can be found here: http://jsfiddle.net/n7Vmr/

Answer 1

You can just change the domain of the scale used to draw the y-axis, look for the line
y.domain(d3.extent(data, function(d) { return d[1]; }));
needs to be changed, if you want it one less than the smallest value in your dataset use
y.domain([d3.min(data, function (d) { return d[1]; })-1, maxValue]);
or if you want it to start from 0, regardless of the data
y.domain([0, maxValue]);