Charting with Google

Charting with
Google

Thursday, March 24, 2011

http://bit.ly/googlechartlinks
Follow along with a list of all the links mentioned


Russell Heimlich (Like the Maneuver)
★ Sole Developer at the
Pew Research Center

★ 3 Years at U.S.News
& World Report

★ Creator of
Dummyimage.com

★ Left handed!


How Can Google Help Us Make Charts?
★ DataTable Object
★ Interactive Charts
(Visualization API)

★ Image Charts
(Chart API)


Getting Started
You have to start somewhere...

http://www.flickr.com/photos/npobre/2601582256/


Load Some Libraries

<script src="http://www.google.com/jsapi"></script>

<script type="text/javascript">
// Load the Visualization API and the piechart package.
google.load('visualization', '1', {'packages':['corechart']});

// Set a callback to run when everything is loaded.
google.setOnLoadCallback(drawChart);

function drawChart() {
// MAGIC!
}
</script>

DataTable Object
Like a database in JavaScript


What is a DataTable?
★ Representation of your data in JavaScript
★ Query just like SQL
★ Sortable, Filterable, Cloneable, Manipulatable
★ Easy to pass along to different visualizations


Making a DataTable
var data = new google.visualization.DataTable();

data.addColumn('string', 'Task');
data.addColumn('number', 'Hours');

data.addRows([
['Work', 11],
['Eat', 1],
['Commute', 2],
['Watch TV', 3]
]);


More Ways To Populate Data
// Create and populate the data table.
  var data = new google.visualization.DataTable();
  data.addColumn('string', 'Task');
  data.addColumn('number', 'Hours per Day');

data.addRows(4);

data.setValue(0, 0, 'Work'); //row index, cell index, value
  data.setValue(0, 1, 11);
  data.setValue(1, 0, 'Eat');
  data.setValue(2, 0, 'Commute');
  data.setValue(3, 0, 'Watch TV');


Which Looks Like This

Task Hours
Work 11

Eat 1

Commute 2

Watch TV 3


DataViews
★ Subset of data from a DataTable
★ Remove or duplicate rows or columns
★ Original DataTable stays intact
★ Live view of the underlying data, not a copy


Making A DataView
var view = new google.visualization.DataView(data);

view.setRows(
view.getFilteredRows([{
column:1,
maxValue:5
}])
);


Our DataView Now Looks Like This

Task Hours

Eat 1

Commute 2

Watch TV 3


Building Interactive Charts
Getting Nitty Gritty


Let’s Make A Pie Chart
// Create and draw the visualization.
var target = document.getElementById('visualization');
new google.visualization.PieChart(target).draw(
view,
{title: ‘So, how was your day?’}
);


And Play With Different Properties
new google.visualization.PieChart(target).draw(
view,
{
title: ‘So, how was your day?’,
is3D: true,
colors: ['#0099ff', '#00ff99', '#9900ff']
}
);


Putting It All Together: Music Age Demo
★ Scrape data from an
HTML table and put it
into a DataTable

★ Dynamically create a
legend for choosing
what to graph

★ Make line graphs and
bar charts from
selected data points

Table Scrapin’ Fun
var tableHeaders = $('table th');
var tableData = $('table tbody tr');
data = new google.visualization.DataTable();

for (i=0; i<tableHeaders.length; i++) {
var cell = tableHeaders[i].innerHTML;
var cellType = 'number';
if (i==0) {
cellType = 'string';
}
data.addColumn(cellType, cell);
}


More Table Scrapin’ Fun
for (i=0; i<tableData.length; i++) {
var row = $(tableData[i]).children();
var rowData = new Array();
for (j=0; j<row.length; j++) {
var cell = row[j].innerHTML;
if (!cell.match(/[a-zA-Z_.-?!+]/)) {
cell = Number(cell)
}
rowData.push(cell);
}
data.addRow(rowData);
}


Preppin’ The View
var artists = $('#legend li');
var selectedArtists = [0];

$('table .on').removeClass('on');
$('table tr').children(':nth-child(1)').addClass('on');

for (i=0; i<artists.length; i++) {
if (!$(artists[i]).hasClass('off')) {
selectedArtists.push(i+1);
$('table tr').children(
':nth-child('+ (i+2) +')'
).addClass('on');
}
}

var view = new google.visualization.DataView(data);
view.setColumns(selectedArtists);

Drawin’ The Line Chart
$('#line').html('');
var lineChart = new google.visualization.LineChart(
document.getElementById('line')
);

lineChart.draw(view, {
width: 500,
height: 350,
enableTooltip: true,
showCategories: true,
legend: 'none',
max: 75,
pointSize: 5
});


Drawin’ The Bar Chart
$('#bar').html('');
var chart = new google.visualization.ColumnChart(
document.getElementById('bar')
);

chart.draw(view, {
width: 500,
height: 350,
enableTooltip: true,
showCategories: true,
legend: 'none',
max: 75,
is3D: true
});


Constructing Static Charts
Time to put your thinking cap on


What is the Google Chart API?
“The Google Chart API lets you dynamically
generate charts with a URL string. You can embed
these charts on your web page, or download the
image for local or offline use.”

–– Google Chart Documentation


Build a URL,
Get a Chart


What types of charts can you make?


Every Chart Starts With A URL
http://chart.googleapis.com/chart?

Parameters come after the question mark
separated by ampersands (&)

The order of parameters doesn’t matter


Requires 3 Things
★ Chart Type (cht=<chart type>)
★ Chart Size (chs=<width>x<height>)
★ Data (chd=<data string>)

★ http://chart.googleapis.com/chart?
cht=p3&chs=250x100&chd=t:60,40


Data Formats
★ Basic Text Format (chd=t:)
★ Simple Encoding (chd=s:)
★ Extended Encoding (chd=e:)

★ Some formats use less characters than others.


Basic Text Data Format
★ Floating Point Values From 0-100
★ Values less than 0 are considered NULL
★ Values higher than 100 are truncated to 100
★ What you see is what you get
★ Ideal for smaller datasets
★ Produces the largest number of characters


Basic Text Data Example
★ chd=t:_30,-30,50,80,200


Simple Encoding Data Format
★ Integer values 0-61
★ Relative Scaling
★ Low Granularity
★ Each value encoded as a single alphanumeric
character
★ Produces the smallest number of characters


Simple Encoding Function
var simpleEncoding =
'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789'

//Scales submitted values so that maxVal becomes the highest.
function simpleEncode(valueArray, maxValue) {
var chartData = ['s:'];
for (var i = 0; i < valueArray.length; i++) {
var currentValue = valueArray[i];
if (!isNaN(currentValue) && currentValue >= 0) {
chartData.push(simpleEncoding.charAt(
Math.round((simpleEncoding.length-1) *
currentValue / maxValue))
); }
else { chartData.push('_'); }
}
return chartData.join('');
}

Simple Encoding Example
★ chd=t:1,19,27,53,61,-1|12,39,57,45,51,27
★ chd=s:BTb19_,Mn5tzb


Extended Data Format
★ Integer values 0-4095
★ Relative scaling
★ High Granularity
★ Each value encoded as
two alphanumeric characters


Extended Encoding Function
Similar to Simple Encoding Function
but too big to show here.

Grab it at
http://code.google.com/apis/chart/docs/
data_formats.html#encoding_data


Extended Encoding Example
★ chd=t:90,1000,2700,3500|3968,-1,1100,250
★ chd=e:BaPoqM2s,-A__RMD6


Data Scaling
★ chds=<min-value>, <max-value>
★ Related to the data format you use!


Axis Scaling
★ chxr=<axis_index>,<start_val>,<end_val>,
<opt_step>

★ Axis labels are not calculated to reflect chart
data automatically! (We do that ourselves)

★ If you’re data is 0-100, then you’re good!


Axis Scaling Example


Year In The News Interactive
★ Load a bunch of data
into a DataTable

★ User selects which
data points they want
to see

★ Render a series of
static Google Charts

★ Shareable Charts

Official Documentation
★ DataTable & DataView Docs
★ Google Visualization API
★ Google Charts API


Chart Tools
★ Chart Wizard
Easy Interface for Building Charts

★ Live Chart Playground
Easy way to edit parameters

★ Google Code Playground
Online Charting Development Environment

More Links
★ Easy Graphs with Google Chart Tools|Nettuts+

★ jQuery Google Chart Plugin

★ List of Google Chart Wrappers

★ Animating Static Google Charts


Sharing Is Caring
★ Grab everything from this presentation via SVN
http://svn.kingkool68.com/projects/google-
charting-api/

★ List of Links Mentioned

★ Stay in Touch @kingkool68 or Facebook or
shoot me an e-mail

And
Remember...


Play and Have Fun!
It’s the only way to learn.


Thank You!
Please say hi to me later,
share your thoughts,
and ask questions.


Charting with Google

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