code: function quartiles( vector ) {
  		var qValues = new Array( 2 ),
  			vec;
  
  		// Create a copy of the input vector:
  		vec = vector.slice();
  
  		// Sort the input vector:
  		vec.sort( function ( a, b ) {
  			return a - b;
  		});
  
  		qValues[ 0 ] = quantile( vec, 0.25 );
  		qValues[ 1 ] = quantile( vec, 0.75 );
  		
  		return qValues;
  	}
docs: end METHOD transform() 
  FUNCTION: quartiles( vector )
  Computes quartiles for a 1d dataset array.
  
  @private
  @param {array} vector - 1d array
  @returns {array} quartiles as a 2-element array