## Errorbars

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 errorbar 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 errorbars
         plot 'file' using 1:2:(sqrt($1)) with xerrorbars
         plot 'file' using 1:2:($1-$3):($1+$3):4:5 with xyerrorbars

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. To get lines plotted between the data points, plot the data file twice, once with errorbars and once with lines (but remember to use the notitle option on one to avoid two entries in the key). Alternately, use the errorlines command (see errorlines (p. )).

The tic marks at the ends of the bar are controlled by set errorbars.

If autoscaling is on, the ranges will be adjusted to include the error bars.

See also http://www.gnuplot.info/demo/mgr.html`errorbar demos.`

See plot using (p. ), plot with (p. ), and set style (p. ) for more information.