4.1.4 Error Bars

In Gnuplot, when one uses errorbars, one can specify either the size of the errorbar, or the minimum to maximum range of the errorbar. Both of these usages share a common syntax, and Gnuplot’s behaviour depends upon the number of columns of data provided:

plot 'data.dat' with yerrorbars

Given a data file with three columns, this takes the third column to indicate the size of the $y$-errorbar. Given a four-column data file, it takes the third and fourth columns to indicate the minimum to maximum range to be marked out by the errorbar.

To avoid confusion, a different syntax is adopted in PyXPlot. The syntax:

plot 'data.dat' with yerrorbars

always assumes that the third column of the data file indicates the size of the errorbar, regardless of whether a fourth is present. The syntax:

plot 'data.dat' with yerrorrange

always assumes that the third and fourth columns indicate the minimum to maximum range of the errorbar.

For clarity, a complete list of the errorbar plot styles available in PyXPlot is given below:

yerrorbars

Vertical errorbars; size drawn from the third data column.

xerrorbars

Horizontal errorbars; size drawn from the third data column.

xyerrorbars

Horizontal and vertical errorbars; sizes drawn from the third and fourth data columns respectively.

errorbars

Shorthand for yerrorbars.

yerrorrange

Vertical errorbars; minimum drawn from the third data column, maximum from the fourth.

xerrorrange

Horizontal errorbars; minimum drawn from the third data column, maximum from the fourth.

xyerrorrange

Horizontal and vertical errorbars; horizontal minimum drawn from the third data column and maximum from the fourth; vertical minimum drawn from the fifth and maximum from the sixth.

errorrange

Shorthand for yerrorrange.