Filtering allows you to dice by selecting a range of the datacube to in the output sheet. If you filter the x or y axes, then a pair of calipers is drawn on the axis, allowing you to specify the range of data you wish to consider.
If you filter by value, then a histogram control opens up on the right of the Ravel control window. You may then drag the maximum and minimum to control the maximum and minimum thresholds of data to be included in the output sheet. This can be used to rapidly locate where particular data values occur within the datacube.