Library /sys$common/syshlp/pca$help.hlb PLOT, Bucket selection qualifiers, /ZEROS  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /ZEROS
       /NOZEROS

    Determines whether zero data count buckets are omitted from
    the histogram. The /NOZEROS qualifier specifies that buckets
    with zero data counts be omitted from the histogram. Thus, the
    histogram becomes smaller since buckets without data are dropped.
    The /ZEROS qualifier retains buckets with zero data counts.

    Note that /NOMAXIMUM, /NOMINIMUM, and /ZEROS are the default
    bucket selection qualifiers.