gnuplot documentation

60 PLOT gnuplot 4.3 77
60.4 Errorlines
Lines with error bars are supported for 2D data file plots by reading one to four additional columns (or
using entries); these additional values are used in different ways by the various errorlines styles.
In the default situation, gnuplot expects to see three, four, or six numbers on each line of the data file
— either
(x, y, ydelta),
(x, y, ylow, yhigh),
(x, y, xdelta),
(x, y, xlow, xhigh),
(x, y, xdelta, ydelta), or
(x, y, xlow, xhigh, ylow, yhigh).
The x coordinate must be specified. The order of the numbers must be exactly as given above, though
the using qualifier can manipulate the order and provide values for missing columns. For example,
plot ’file’ with errorlines
plot ’file’ using 1:2:(sqrt($1)) with xerrorlines
plot ’file’ using 1:2:($1-$3):($1+$3):4:5 with xyerrorlines
The last example is for a file containing an unsupported combination of relative x and absolute y errors.
The using entry generates absolute x min and max from the relative error.
The y error bar is a vertical line plotted from (x, ylow) to (x, yhigh). If ydelta is specified instead of
ylow and yhigh, ylow = y - ydelta and yhigh = y + ydelta are derived. If there are only two numbers
on the record, yhigh and ylow are both set to y. The x error bar is a horizontal line computed in the
same fashion.
The error bars have crossbars at each end unless set bars is used (see set bars (p. 88) for details).
If autoscaling is on, the ranges will be adjusted to include the error bars.
See plot using (p. 74), plot with (p. 79), and set style (p. 130) for more information.
60.5 Parametric
When in parametric mode (set parametric) mathematical expressions must be given in pairs for plot
and in triplets for splot.
Examples:
plot sin(t),t**2
splot cos(u)*cos(v),cos(u)*sin(v),sin(u)
Data files are plotted as before, except any preceding parametric function must be fully specified before
a data file is given as a plot. In other words, the x parametric function (sin(t) above) and the y
parametric function (t**2 above) must not be interrupted with any modifiers or data functions; doing
so will generate a syntax error stating that the parametric function is not fully specified.
Other modifiers, such as with and title, may be specified only after the parametric function has been
completed:
See also
plot sin(t),t**2 title ’Parametric example’ with linespoints
Parametric Mode Demos.
60.6 Ranges
The optional ranges specify the region of the graph that will be displayed.
Syntax: