A CodePen by Marcelo Paiva. D3.005 Linear Scale - In this pen let's understand the scale function and its applications. It's very unlikely that the values in any 
data set will fit perfectly inside the SVG area; let's say 
that your bar has a 850 pixel width, but your available SVG
are is only 400 pixels, when you render the rectangle the 
bar will exceed the 400px area and won't be shown.

D3 Scale functions provide ways to fit the extending
elements proportially inside the available SVG area.