Controls

• d3.svg.brush - click and drag to select one- or two-dimensional regions.
• brush - apply a brush to the given selection or transition.
• brush.x - the brush’s x-scale, for horizontal brushing.
• brush.y - the brush’s y-scale, for vertical brushing.
• brush.extent - the brush’s extent in zero, one or two dimensions.
• brush.clear - reset the brush extent.
• brush.empty - whether or not the brush extent is empty.
• brush.on - listeners for when the brush is moved.
• brush.event - dispatch brush events after setting the extent.