#### Pseudocolumns

Expressions in the using clause of a plot statement can refer to additional bookkeeping values in addition to the actual data values contained in the input file. These are contained in `"`pseudocolumns`"`.

         column(0)   The sequential order of each point within a data set.
                     The counter starts at 0 and is reset by two sequential blank
                     records.  The shorthand form $0 is available.
         column(-1)  This counter starts at 0 and is reset by a single blank line.
                     This corresponds to the data line in array or grid data.
         column(-2)  The index number of the current data set within a file that
                     contains multiple data sets.  See `index`.