errbar add vertical error bars on a 2D plot

## Syntax

    errbar(x, y, em, ep)

## Arguments

x, y, em, ep

  four matrices of the same size.

## Description

`errbar` adds vertical error bars on a 2D plot. `x` and `y` have the same meaning as in `plot2d`.

`em(i,j)` and `ep(i,j)` stands for the error interval on the value `y(i,j)`: `[y(i,j)-em(i,j),y(i,j)+ep(i,j)]`.

Enter the command `errbar()` to see a demo.

## Examples

    t=[0:0.1:2*%pi]';
    y=[sin(t) cos(t)]; x=[t t];
    plot2d(x,y)
    errbar(x,y,0.05*ones(x),0.03*ones(x))

t=[0:0.1:2*%pi]'; y=[sin(t) cos(t)]; x=[t t]; plot2d(x,y) errbar(x,y,0.05*ones(x),0.03*ones(x))

## See also

- plot2d