status.i4.v = wn_data_extrema(min_x.r4.r, max_x.r4.r,
				      min_y.r4.r, max_y.r4.r)

	This routine finds the minimum and maximum values for the
	the saved data set for the active graphic window.

	min_x		returned minimum x value
	max_x		returned maximum x value
	min_y		returned minimum y value
	max_y		returned maximum y value

	This function returns ACNET status values as follows:

	OK			success
	CBS_NOSETUP		an active window has not been established
				or no data has been saved

	This function requires the following include files:

	cbslib_h, acnet_errors_h

	Related functions:

	wn_data_save(_c), wn_data_set_cut_c, wn_data_mean, wn_data_recall,
	wn_data_query, wn_data_polyfit_c, wn_data_fft_c, intro_graphics_windows

	C/C++ usage:

	int	status;
	float	min_x;
	float	max_x;
	float	min_y;
	float	max_y;

	status = wn_data_extrema(&min_x,&max_x,&min_y,&max_y);