 Discrete data contained in a file can be displayed by specifying the name of
 the data file (enclosed in single or double quotes) on the `plot` command line.

 Syntax:
       plot '<file_name>' {index <index list>}
                             {every <every list>}
                             {thru <thru expression>}
                             {using <using list>}
                             {smooth <option>}

 The modifiers `index`, `every`, `thru`, `using`, and `smooth` are discussed
 separately.  In brief, `index` selects which data sets in a multi-data-set
 file are to be plotted, `every` specifies which points within a single data
 set are to be plotted, `using` determines how the columns within a single
 record are to be interpreted (`thru` is a special case of `using`), and
 `smooth` allows for simple interpolation and approximation.  ('splot' has a
 similar syntax, but does not support the `smooth` and `thru` options.)

 Data files should contain at least one data point per record (`using` can
 select one data point from the record).  Records beginning with `#` (and
 also with `!` on VMS) will be treated as comments and ignored.  Each data
 point represents an (x,y) pair.  For `plot`s with error bars (see `set style
 errorbars`), each data point is (x,y,ydelta), (x,y,ylow,yhigh), (x,y,xdelta),
 (x,y,xlow,xhigh), or (x,y,xlow,xhigh,ylow,yhigh).  In all cases, the numbers
 on each record of a data file must be separated by white space (one or more
 blanks or tabs), unless a format specifier is provided by the `using` option.
 This white space divides each record into columns.

 Data may be written in exponential format with the exponent preceded by the
 letter e, E, d, D, q, or Q.

 Only one column (the y value) need be provided.  If x is omitted, `gnuplot`
 provides integer values starting at 0.

 In datafiles, blank records (records with no characters other than blanks and
 a newline and/or carriage return) are significant---pairs of blank records
 separate `index`es (see `plot datafile index`).  Data separated by double
 blank records are treated as if they were in separate data files.

 Single blank records designate discontinuities in a `plot`; no line will join
 points separated by a blank records (if they are plotted with a line style).

 If autoscaling has been enabled (`set autoscale`), the axes are automatically
 extended to include all datapoints, with a whole number of tic marks if tics
 are being drawn.  This has two consequences: i) For `splot`, the corner of
 the surface may not coincide with the corner of the base.  In this case, no
 vertical line is drawn.  ii) When plotting data with the same x range on a
 dual-axis graph, the x coordinates may not coincide if the x2tics are not
 being drawn.  This is because the x axis has been autoextended to a whole
 number of tics, but the x2 axis has not.  The following example illustrates
 the problem:

       reset; plot '-', '-'
       1 1
       19 19
       e
       1 1
       19 19
       e

Subtopics available for plot datafile:
    every             example           index             smooth
    special-filenames thru              using

