GRAPH:error_bars

symmetric

 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

 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. The error bar will be clipped at the boundaries
 of the plotting symbol if the symbol is symmetric under 90 degree
 rotations, for example, a box (symbol number 1).