Turns off plot grids.
GRIDOFF(win1, win2, ..., winN)
Optional. Zero or more windows. Defaults to the current window.
displays horizontal, dashed grids when a series is displayed.
Use gridoff to turn the grids off.
gridoff(w1, w3, w4)
Turns off plot grids in W1, W3 and W4.
See SETGRIDSTYLE to set the style of a specified grid.