Rgviz-rails¶ ↑

This library makes it easy to implement a Visualization data source so that you can easily chart or visualize your data from ActiveRecord models or from in-memory arrays. The library implements the Google Visualization API wire protocol.

It also allows you to render the visualizations in a view template in a very simple but powerful way.

This library is built on top of rgviz.

Installation¶ ↑

gem install rgviz-rails

Rails 3¶ ↑

In your Gemfile

gem 'rgviz'
gem 'rgviz-rails', :require => 'rgviz_rails'

Rails 2.x¶ ↑

In your environment.rb

config.gem "rgviz"
config.gem "rgviz-rails", :lib => 'rgviz_rails'

Usage¶ ↑

To make a method in your controller be a visualization API endpoint:

class VizController < ApplicationController

  def person
    # Person is an ActiveRecord::Base class
    render :rgviz => Person
  end

end

So for example if Person has name and age, pointing your browser to:

http://localhost:3000/viz/person?select name where age > 20 limit 5

would render the necessary javascript code that implements the Google Visualization API wire protocol.

Extensions¶ ↑

To enable the extensions defined by rgviz you need to specify it in the render method:

render :rgviz => Person, :extensions => true

Associations¶ ↑

If you want to filter, order by or group by columns that are in a model’s association you can use underscores. This is better understood with an example:

class Person < ActiveRecord::Base
  belongs_to :city
end

class City < ActiveRecord::Base
  belongs_to :country
end

class Country < ActiveRecord::Base
end

To select the name of the city each person belongs to:

select city_name

To select the name of the country of the city each person belongs to:

select city_country_name

A slightly more complex example:

select avg(age) where city_country_name = 'Argentina' group by city_name

The library will make it in just one query, writing all the SQL joins for you.

Extra conditions¶ ↑

Sometimes you want to limit your results the query will work with. You can do it like this:

render :rgviz => Person, :conditions => ['age > ?', 20]

Or also:

render :rgviz => Person, :conditions => 'age > 20'

Preprocessing¶ ↑

If you need to tweak a result before returning it, just include a block:

render :rgviz => Person do |table|
  # Modify the Rgviz::Table object
end

Showing a visualization in a view¶ ↑

You can invoke the rgviz method in your views. Read more about this.

You can always do it the old way.

Executing queries over in-memory arrays¶ ↑

You can also apply a query over an array of arrays that contains your “records” to be queried.

types = [[:id, :number], [:name, :string], [:age, :number]]
records = [
  [1, 'John', 23],
  [2, 'Pete', 36]
]
executor = Rgviz::MemoryExecutor.new records, types

render :rgviz => executor

This is very useful if you need to present visualizations against data coming from a CSV file.

Current Limitations¶ ↑

• The format clause works, but formatting is as in ruby (like “%.2f” for numbers, “foo %s bar” for strings, and “%Y-%m-%d” for dates, as specified by Time#strftime)

• Only supports MySQL, PostgreSQL and SQLite adapters

• These scalar functions are not supported for SQLite: millisecond, quarter

• These scalar functions are not supported for MySQL: millisecond

• The function toDate doesn’t accept a number as its argument

• The tsv output format is not supported

Contributors¶ ↑

• Brad Seefeld