Teach Yourself D3.js

D3 is a JavaScript framework used for data visualization.
Learning how to work with D3.js is very easy. If you begin with the basics, you’ll see how easy it is to use D3, because:

  • the DOM function names are much shorter than those in the legacy DOM library.
  • the same functions are used for both setting and getting values.
  • setters return a value, so you can keep working with the same element without repeating its name.

If you already know some framework, you probably feel that there’s nothing new under the sun, which is good because it makes learning the new stuff easier.

So, What’s New?

In D3, you can:
* add and remove SVG and HTML elements using the setters and getter.
* set and get the element’s properties, attributes, styles, text and… data

Getting Started

First, download the framework from http://d3js.org
After you include it in your script, you can use selections, that is wrappers for elements.
To get a selection, use one of the functions:

  • d3.select(selector) – to select the first element matching selector.
  • d3.selectAll(selector) – to select the all elements matching selector.

Like the d3 object, selections has their select and selectAll methods to select descendant.

If selection is a selection, it’s easy to understand what selection.text(), selection.attribute(), selection.style(), selection.insert(), and selection.append() do. But, what does selection.data() do?

Data And Update Selection

The selection’s method data() helps you use the HTML DOM as a database.
selection.data() returns an array of all data that belongs to the elements of the selectionץ The data is held in the property __data__ of the element.
selection.data(arr, func) – defines an update selection and distribute the elements of array arr to the elements of selection.
func(d,i)is a function that:

  • receives d an element of arr and its index i.
  • returns a record key.

If func is not passed, the key is the element’s index.

A recommended way to create an update selection is:
var updSelection = selection1.selectAll(selector).data(arr)

Now, updSelection is a selection of existing elements whose data has been changed.
In addition, updSelection has to methods:

  • updSelection.enter() – returns place holders for elements to be created under selection1.
  • updSelection.exit()– returns elements that have lost their data, and are usually to be removed.

Using the data

The methods attr, style, property, text and data can accept a function as a value to set. The function will be called for each element of the selection’s data. And its arguments will be the array element and its index.

Now, let us see it in an example.
The following code arranges data in a donut layout::

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-type" content="text/html; charset=utf-8">
<title>Testing Pie Chart</title>
<script type="text/javascript" src="d3.min.js"></script>

<style type="text/css">
.slice text {
font-size: 12pt;
font-family: Arial;
}
</style>
</head>
<body>
<script type="text/javascript">
var width = 300, 
    height = 300, 
    radius = 100, 
    color = d3.scale.category20c(); //builtin range of colors


// Step 1: creating a container for the donut chart, and attach raw data to it.
var vis = d3.select("body")
            .append("svg")     //create the SVG element inside the <body>
            .datum([{"label":"first", "value":20},
                    {"label":"second", "value":10},
                    {"label":"third", "value":30},
                    {"label":"fourth", "value":25}])       
            .attr({"width": width, "height": height})  
            .append("g")
            .attr("transform", "translate(" + radius + "," + radius + ")") //move the center of the pie chart from 0, 0 to r, r



// Step two: defining the accessors of the layour function. 
//           The function 'pie' will use the 'value' accessor to compute the arc's length.
var pie = d3.layout.pie() 
            .value(function(d) { return d.value; })
            .sort(function(a,b){return a.label<b.label?-1:a.label==b.label?0:1;});

// Step 3: Create the update selection. 
var updateSelection = vis.selectAll("g") 
                         .data(pie);    // This will use the function 'pie' to create arc data from the row data attached to the visualisation element.


// Step 4: Using the data in the update selection to create shape elements.
var arc = d3.svg.arc() 
            .outerRadius(radius)
            .innerRadius(radius / 2)
;
updateSelection.enter()
               .append('g')
               .attr('class','slice')
               .append("path")
               .style("fill", function(d, i) { return color(i); } ) //set the color for each slice to be chosen from the color function defined above
               .attr("d", arc);                                     // Create the arc from the arc data attached to each element.

updateSelection.append("text") 
               .attr("transform", 
                     function(d) { 
                       return "translate(" + arc.centroid(d) + ")"; 
                     })
               .attr("text-anchor", "middle")                  
               .text(function(d, i) { return d.data.label; }); 


</script>
</body>
</html> 

And following is the chart:
enter image description here

For more funcions, see the API Reference.

Advertisements

Sending Drupal Mail From Your GoDaddy Server

I have an account on Godaddy.com. This site allows its user to install products such as Drupal. Drupal is a 3rd-party PHP framework that can be installed automatically by web hosting sites. Sites built with Drupal can have registered users, and when a users signs up, they get confirmation e-mails. But the site does not send out e-mails yet. It should be configured1 specifying the e-mail address at ‘Home » Administration » Configuration » System’ is NOT enough. The PHP function ‘mail’ works properly, but if you try to find where drupal uses that function, it does not. Drupal invokes the system shell command ‘sendmail’ instead.

Searching what else I should do I found, that there is a module named SMTP, that can be downloaded from here.

Time to configure the SMTP module. I try to find the value for the field ‘SMTP Server’, but the value found in the E-Mail Setup Center was not helpful.

So, I tried to ask the Godaddy Support Team how the heck to configure SMTP, and got the following response

:Dear Amit,

Thank you for contacting Online Support in regards to Drupal.

Unfortunately we are unable to provide direct troubleshooting or support for 3rd party applications such as Drupal. I would suggest that you consult your favorite search engine for further assistance.

So, I tried to find a solution using Google. It was not very easy, but, eventually, I found that the server name is “relay-hosting.secureserver.net”. the port is 25, and no encryption protocol should be in use. The username and password should remain empy.

This is an old issue, I found it here, and I believe that the support team should come up with better responses than they sent me.

 

Communication Between Backbone.js And PHP

Backbone.js is a Javascript framework known as MV* (Model, View and stuff). This framework has the Backbone.sync function to perform CRUD (Create, Read, Update, Delete) operations. In order for a model object to perform these operations, it should have a property named ‘url’. The ‘sync’ function receives 3 arguments: method, model and options. Model objects also have functions that call the ‘sync’ functions, these functions are: ‘fetch’, ‘save’ and ‘destroy’. The function Save does both Create and Update operation: If the property idAttribute is defined, and the idAttribute is set, ‘save’ sends an update request, otherwise it sends a ‘create’ request. The content type of the request is ”application/json”.

How Does The Server Know What Request Type It Receives?

The client-side developer specifies one ‘url’ only per model. The server-side program can determine the type by checking the value of $_SERVER[‘REQUEST_MOTHED’]:

  • ‘GET’ – a read (or fetch) request.
  • ‘POST’ – a create(save a new model) request.
  • ‘PUT’ – an update(save existing model’s detail) request.
  • ‘DELETE’ – a delete(destroy) request.

What To Send and How To Read?

Backbone.sync uses AJAX to send requests to the server. What you have to pass is the method and model. You better not skip the 3rd arguments, options, which contains at least two member:

  • ‘success’ – a function called when the server processes the request successfully.
  • ‘error’ – a function called when the server fails to process the request.

For example:

Backbone.sync(‘GET’, myModel, {

success: function(resp){

// process the response

},

error: function(resp){

// Recover or print an error message.

}

});

If you call Backbone.sync from an object don’t use ‘this” inside the success and error function as a reference to your object.

For example, if you call ‘sync’ from a view, write ‘myView=this;’ before your call to the ‘sync’ function.

Read Requests

If you send a ‘fetch’ request, specify ‘data’ in the ‘options’ argument, for example:

myModel.fetch({

data: {‘attr1′:’value1’, ‘attr2′:’value2’, … , ‘attrN’:”valueN’},

success:

….

error:

});

In the Server Side

The request attributes are taken from $_GET or $_REQUEST, as usual.

Save Requests

Send the attributes and the options.

For example:

myModel.save(myModel.attributes, {

success:

error:

….

});

In The Server Side

The data should be read from the file “php://input”, a filename used for reading data from the request body. The content is a string, and should be parsed, but since the incoming request data is JSON encoded, you should use the PHP method “json_decode”.

For example:

$post_vars = json_decode(file_get_contents(‘php://input’), true);

Destroy Requests

This time, you should set the ‘data’ member of the options argument to a JSON string. For example:

Backbone.sync(‘delete’, myModel,{
data: JSON.stringify(myModel),  // This time the developer encodes the data.

success: function(model, resp) {

…..

},

error: function(){

….

} );

In The Server Side

Read the data from ‘http://input&#8217; and decode it using json_decode. For example:

$post_vars = json_decode(file_get_contents(‘php://input’), true);

Anyways …

You can make sure you read the data correctly by sending the contents of ‘$_SERVER’, $post_vars and ‘$_REQUEST’ to the error_log. To print an array use json_encode.

Sending a Response To the Client

The response is everything the server side application prints to the standard output. You should print your response data encoded into JSON, as follows:

echo json_encode(responsedata);

Reading a Response

The response returned from the server is the first argument passed to the ‘succss’ callback function. It is not a model object, and you should get values from there using the method ‘get(attr-name’ or the member ‘attributes’.

For example:

{success: function(msg){
switch (msg.get(‘status’)){  // Get the value of the attribute ‘status’ in the server’s response.

To debug your code, you can use ‘alert(JSON.stringify(msg));’.