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 plots 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 indexes (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