D3.js

Data-Driven Documents

Slides : bit.ly/gdi-d3-slides

What is D3?

What d3 is not?

Not a prototyping tool.

Then Why?

Lot's of examples

How to D3

Procedure to associate data with DOM

1. Select a parent container and child nodes
2. Bind array of data to child nodes
3. Append nodes to parent container
4. Bind events, style and animate!

Selection

Select a parent container and child nodes

jQuery

						var paragraphs = $("div p");
					

D3

						var paragraphs = d3.select("div").selectAll("p");
					

D3 difference: child nodes might not actually exist

Selectors in D3 are declared the same way as CSS rules. An important difference is that a D3 selector object only contains the elements that matched the selection rule when the selection was first created.

Data

Bind array of data to child nodes

						d3.selectAll("p")
							.data([3, 7, 21, 31, 35, 42])
					

JSFiddle

Enter() and Append()

When data is bound to a selection, each element in the data array is paired with the corresponding node in the selection. If there are fewer nodes than data, the extra data elements form the enter selection, which you can instantiate by appending to the enter selection

						d3.select("body").selectAll("p")
								.data([3, 7, 21, 31, 35, 42])
							.enter().append("p");
					

JSFiddle

Exit() and Remove()

Using D3’s exit and remove, you can get rid of outgoing nodes that are no longer needed.

var bars = d3.select('svg').selectAll('rect').data(someData);

//if we have more data, add new rectangles for those data items
bars.enter().append('rect')

//if we have less data points, remove the rectangles that no longer have a data pairing.
bars.exit().remove();
					

if you forget about the enter and exit selections, you will automatically select only the elements for which there exists corresponding data.

// Update…
var p = d3.select("body").selectAll("p")
	.data([3, 7, 21, 31, 35, 42]);

// Enter…
p.enter().append("p")

// Exit…
p.exit().remove();
					

By handling these three cases separately, you specify precisely which operations run on which nodes.

Let's give it a try

Exercise: http://bit.ly/enter-exit-exercise

If you get stuck...Sotlution

You can operate over the nodes in a declarative way using selector methods.

• setting attributes or styles
• registering event listeners
• adding, removing or sorting nodes
• and changing HTML or text content

Style

You can use data values or index in a callback to define any property.

d3.select("div").selectAll("p").style("color", function(data, i) {
	return i % 2 ? "red" : "blue";
});
					

JSFiddle

Transition

d3.selectAll("circle")
	.attr("r", "0");
	.transition()
	.duration(750)
	.delay(function(d, i) { return i * 10; })
	.attr("r", function(d) { return Math.sqrt(d); });
					

Try it for yourself

Exercise 0: Look at the example and create a transition to change the size of the circles:http://bit.ly/d3-transitions

Exercise 1: http://bit.ly/d3exercise1

In case you get stuck... Solution for Exercise 1

More Advanced D3

Scales and Domains

Axis

Loading external data

Scales

Scales transform a number in a certain interval (called the domain) into a number in another interval (called the range).

• d3.scale.linear - construct a linear quantitative scale.
• domain - get or set the scale's input domain.
• range - get or set the scale's output range.

Quantitative Scale

• Linear scales
• Logarithmic scales
• Power scales (including square root scales)

var x = d3.scale.linear()
		.domain([0, d3.max(data)])
		.range([0, 420]);
d3.select(".chart")
	.selectAll("div")
		.data([3, 7, 21, 31, 35, 42])
	.enter().append("div")
		.style("width", function(d) { return x(d) + "px"; })
					

Ordinal Scale

Ordinal Scale have a discrete domain, such as a set of names or categories.

var x = d3.scale.ordinal()
	.domain(["A", "B", "C", "D", "E", "F"])
	.rangeRoundBands([0, width], .1);
					

Color Categories

d3.scale.category10() - Constructs a new ordinal scale with a range of ten categorical colors:

JSFiddle

Let's refactor our bar chart.

Solution: Bar Charts with Scale

Axis

d3.svg.axis creates a new axis generator.

• axis.scale
• axis.orient
• axis.ticks
• axis.tickFormat

var xAxis = d3.svg.axis()
    .scale(x)
    .orient('bottom')
    .tickValues(data);
					

Working with Arrays

Most commonly used functions

• d3.min/d3.max
• d3.range
• d3.keys - lists the keys of an associative array.
• d3.merge - merges multiple arrays into one array.
• d3.nest - groups array elements hierarchically.

Loading External Resources

• d3.json
• d3.csv
• d3.tsv

Examples

Bar Chart with tooltip

Pie Chart

Good News!

• NVD3
• C3.js
• Rickshaw

Other D3 resources

• Scott Murray / @alignedleft
• Angular and D3 book by Ari Lerner and Victor Powell
• D3 meet-up group hosted by Ian Johnson
• Jerome Cukier / @jcukier

THE END

BY Aysegul Yonet / aysegulyonet@gmail.com