Adjust error bar width

function errorbar_tick(h,w,xtype)
ERRORBAR_TICK Adjust the width of errorbars

ERRORBAR_TICK(H) adjust the width of error bars with handle H. Error bars width is given as a ratio of X axis lenght (1/80).

ERRORBAR_TICK(H,W) adjust the width of error bars with handle H. The input W is given as a ratio of X axis lenght (1/W). The result is independant of the x-axis units. A ratio between 20 and 80 is usually fine.

ERRORBAR_TICK(H,W,'UNITS') adjust the width of error bars with handle H. The input W is given in the units of the curent x-axis.