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