Error bars

Syntax: GRAPH { `legendtext' } x y { ye1 { xe1 { ye2 { xe2 }}}}

The optional vectors ye1, xe1, ye2, and xe2 are interpreted as errors for drawing error bars. You can have symmetric or asymmetric error bars.

Symmetric error bars

For symmetric error bars, the error variable should contain one half of the total error. See the table below.

parameters present result
ye1 but not ye2 symmetric vertical error bars will be drawn, i.e.,
at the point (x[j],y[j]), the error bar is drawn
from y[j]-ye1[j] to y[j]+ye1[j]
xe1 but not xe2 symmetric horizontal error bars will be drawn, i.e.,
at the point (x[j],y[j]), the error bar is drawn
from x[j]-xe1[j] to x[j]+xe1[j]

Asymmetric error bars

For asymmetric error bars, the first error variable contains the lower error and the second error variable contains the upper error. See the table below.

parameters present result
ye1 and ye2 asymmetric vertical error bars are drawn, i.e.,
at the point (x[j],y[j]), the error bar is drawn
from y[j]-ye1[j] to y[j]+ye2[j]
xe1 and xe2 asymmetric horizontal error bars are drawn, i.e.,
at the point (x[j],y[j]), the error bar is drawn
from x[j]-xe1[j] to x[j]+xe2[j]

Error bar shape

The error bars will have "feet", that is, short line segments, one at each end of the error bar, which are perpendicular to the error bar. The size of the foot is the same as the size of the plotting symbol, which can be changed using the %PLOTSYMBOLSIZE characteristic or by entering a relative size vector with the PLOTSYMBOL characteristic. The error bar will be clipped at the boundaries of the plotting symbol if the symbol is symmetric under 90° rotations, for example, a box (symbol number 1).

Example

  Histograms
  Filling the area under a curve