Provides the d3 class in Mata for constructing D3js graphs. The library is a wrapper around the D3js library and generally has the same semantics as the original library with a few deviations (e.g., the object must first be initialized before any methods can be called, and some of the methods like .svg require empty parentheses with this library .svg() generate the appropriate syntax).
The class also includes an .undo() method which returns the object to its state prior to the last method that was called.
The .cont() method accepts a matrix of d3() class as its argument and appends each of the arguments to one another and places a terminating ';' after the last value in the matrix before returning the string containing the JavaScript code.
The .printer() method also accepts a matrix of d3() class objects, but places a terminating ';' after each value in the matrix before appending all of the values into a single string object.