docs: function onData( accessors ) {
  		var keys = Object.keys( accessors ),
  			numKeys = keys.length,
  			accessor, value;
  		/**
  		* FUNCTION: onData( d )
  		*	Data event handler. Only emits data where accessed data is numeric. If a value cannot be accessed, no data is emitted. Note: if no set accessors, all data is allowed through.
  		*
  		* @param {*} d - data stream datum
  		*/
  		return function onData( d ) {
  			for ( var i = 0; i < numKeys; i++ ) {
  				accessor = accessors[ keys[i] ];
  				try {
  					value = accessor( d );
  				} catch( err ) {
  					return;
  				}
  				if ( !isNumber( value ) ) {
  					return;
  				}
  			}
  			// Queue the data:
  			this.queue( d );
  		}; // end FUNCTION onData()
  	}