Important: The stats package has been deprecated. Use the superseding package Statistics instead.

The notion of gaps is needed for interpolation because classes are usually assumed to extend so that they touch. For example, when specifying that classes go from 1 to 5 and 6 to 10, one usually means that the two classes meet at 5.5.  Therefore, the classes 0..4, 5..9, 10..14

really mean

To specify that the boundaries of classes are not to be changed, specify the gap to be 0.

If the argument gap is not specified, or if it is equal to the keyword false, then the gap is computed from data. The gaps around the lowest class are assumed to be of the same size, as are the gaps around the highest class. If there is only one class, then the gap is assumed to be zero.