code: function( accuIndex, weight ) {
  
  		// note: happily accumulating nothing when weight = 0, the caller knows
  		// the weight and shouldn't have made the call in the first place
  
  		var buffer = this.buffer,
  			stride = this.valueSize,
  			offset = accuIndex * stride + stride,
  
  			currentWeight = this.cumulativeWeight;
  
  		if ( currentWeight === 0 ) {
  
  			// accuN := incoming * weight
  
  			for ( var i = 0; i !== stride; ++ i ) {
  
  				buffer[ offset + i ] = buffer[ i ];
  
  			}
  
  			currentWeight = weight;
  
  		} else {
  
  			// accuN := accuN + incoming * weight
  
  			currentWeight += weight;
  			var mix = weight / currentWeight;
  			this._mixBufferRegion( buffer, offset, 0, mix, stride );
  
  		}
  
  		this.cumulativeWeight = currentWeight;
  
  	}
docs: accumulate data in the 'incoming' region into 'accu<i>'