code: function partial( fn, j ) {
  	return function accessor( d, i ) {
  		return fn( d, i, j );
  	};
  }
docs: FUNCTIONS // 
  FUNCTION: partial( fn, j )
  Partially applied function from the right.
  
  @private
  @param {Function} fn - input function
  @param {Number} j - array index
  @returns {Function} partially applied function