As for `plot`, discrete data contained in a file can be displayed by specifying the name of the data file, enclosed in quotes, on the `splot` command line.
Syntax:
splot '<file_name>' {binary <binary list>}
{matrix}
{index <index list>}
{every <every list>}
{using <using list>}
The special filenames `""` and `"-"` are permitted, as in `plot`.
In brief, `binary` and `matrix` indicate that the data are in a special form, index selects which data sets in a multi-data-set file are to be plotted, every specifies which datalines (subsets) within a single data set are to be plotted, and using determines how the columns within a single record are to be interpreted.
The options index and every behave the same way as with `plot`; using does so also, except that the using list must provide three entries instead of two.
The `plot` options thru and smooth are not available for `splot`, but cntrparam and dgrid3d provide limited smoothing capabilities.
Data file organization is essentially the same as for `plot`, except that each point is an (x,y,z) triple. If only a single value is provided, it will be used for z, the datablock number will be used for y, and the index of the data point in the datablock will be used for x. If two or four values are provided, `gnuplot` uses the last value for calculating the color in pm3d plots. Three values are interpreted as an (x,y,z) triple. Additional values are generally used as errors, which can be used by fit.
Single blank records separate datablocks in a `splot` datafile; `splot` treats datablocks as the equivalent of function y-isolines. No line will join points separated by a blank record. If all datablocks contain the same number of points, `gnuplot` will draw cross-isolines between datablocks, connecting corresponding points. This is termed "grid data", and is required for drawing a surface, for contouring (contour) and hidden-line removal (hidden3d). See also `splot grid_data`.
It is no longer necessary to specify `parametric` mode for three-column `splot`s.