draw grid
egrid([xAxisSouthScale,yAxisWestScale[,xAxisNorthScale,yAxisEastScale]])
xAxisSouthScale :
scale vector of south axis [start step end]
yAxisWestScale :
scale vector of west axis [start step end]
xAxisNorthScale :
scale vector of north axis [start step end]
yAxisEastScale :
scale vector of east axis [start step end]
special cases of scale vectors are
if start=0 and end=0 then autorange=on
if step=0 then autoscale=on
(default scale vector=[0 0 0])