_G_r_a_p_h_i_c_a_l _U_n_i_t_s
	
	     xinch(x=1)
	     yinch(x=1)
	
	_D_e_s_c_r_i_p_t_i_o_n:
	
	     xinch and yinch convert the specified number of inches
	     given as their arguments into the correct units for
	     plotting with graphics functions.
	
	_E_x_a_m_p_l_e_s:
	
	     # plot labels offset 0.2 inches to the right
	     # of plotted symbols in a plot
	     plot(x, y)
	     text(x+xinch(0.2), y, labs, adj=0)