Deepak Jois – Blog

EYODF : Reading chart using gchartrb On Wednesday, December 19, 2007

Labels: books, gchartrb  

EYODF, for those who do not know stands for Eat Your Own Dog Food. Today, I decided to use gchartrb to plot a line chart of the number of books I have read since Jan 2006, an information that I maintain quite religiously using my del.icio.us ‘read’ tag.

It was an enlightening experience, using the stuff that I built myself. Apart from a few things that I noticed were inelegant, I also discovered a few bugs. But first the code. If you want to use the code, you will need the gchartrb and rubilicious gems installed.

require 'rubygems'
require 'rubilicious'
require 'google_chart'

# Retrieve from delicious
r = Rubilicious.new('deepakjois', 'amistupid')
books = r.all('read')

# Create a monthwise breakdown of books read since 2006
books_grouped = []
[2006,2007].each do |year|
  12.times do |month|
       count = books.select {|b| b['time'].year == year and b['time'].month == month+1 }.size
       books_grouped << [ "#{Date::ABBR_MONTHNAMES[month+1]}" ,count]
  end
end

# Create chart
lc = GoogleChart::LineChart.new('600x250', 'Reading Chart 2006-Present', false) 
lc.show_legend = false
lc.data_encoding = :text # more granular
data_series = books_grouped.collect{ |b| b.last } # numerical data
labels = books_grouped.collect{ |b| b.first } # labels
lc.data "", data_series, 'ff0000'
lc.axis :x, :labels => labels, 
            :color => '000000' # Months
            
lc.axis :x, :labels => [2006, 2007], 
            :positions => [0, (12/data_series.size.to_f) * 100], 
            :color => '000000', 
            :font_size => 12 ,
            :alignment => :left # Year
            
lc.axis :y, :labels => (0..data_series.max).to_a, 
            :color => '000000' # Number of books
            
lc.fill :chart, :solid, :color => "ffffff"
lc.fill :background, :solid, :color => 'ffffff'
lc.grid :y_step => 100/(data_series.max.to_f), :x_step => 0, :length_segment => 2, :length_blank => 1

# Adding small black circles as shape markers
data_series.size.times do |i|
  lc.shape_marker :circle, :color => '000000', :data_set_index => 0, :data_point_index => i, :pixel_size => 5 
end
                                              
puts lc.to_url(:chts => '000000,20') # Set title font size and color manually due to bug in gchartrb

This code led to the chart below

I discovered a couple of bugs in gchartrb, apart from a couple of features I missed out due to not reading the API carefully enough.

• The title_color and title_font_size attributes do not work as advertised. Need to fix that ASAP. As a workaround, I have manually added those parameters while calling the to_url method.
• I did not realise that the shape markers and the range markers use the same param name, i.e. chm. If I try to add both using gchartrb, one of them gets overwritten by the other.

Now off to fix those bugs, and implement those features.