_R_o_u_n_d_i_n_g _o_f _N_u_m_b_e_r_s
	
	     ceiling(x)
	     floor(x)
	     round(x, digits=0)
	     signif(x, digits)
	     trunc(x)
	
	_D_e_s_c_r_i_p_t_i_o_n:
	
	     ceiling takes a single numeric argument x and returns a
	     numeric vector containing the smallest integers not
	     less than the corresponding elements of x.
	
	     floor takes a single numeric argument x and returns a
	     numeric vector containing the largest integers not
	     greater than the corresponding elements of x.
	
	     round rounds the values in its first argument to the
	     specified number of decimal places (default 0).
	
	     signif rounds the values in its first argument to the
	     specified number of significant digits.
	
	     trunc takes a single numeric argument x and returns a
	     numeric vector containing the integers by truncating
	     the values in x toward 0.
	
	_S_e_e _A_l_s_o:
	
	     as.integer.
	
	_E_x_a_m_p_l_e_s:
	
	     print(x1 <- seq(-2,4, by =.5))
	     x1[trunc(x1) != floor(x1)]
	     x1[round(x1) != floor(x1 + .5)]
	     all(trunc(x1) == as.integer(x1)) # TRUE
	     non.int <- ceiling(x1) != floor(x1)
	     all(non.int == (ceiling(x1) != trunc(x1) | trunc(x1) != floor(x1))) # TRUE
	     all((signif(x1, 1) != round(x1)) == (non.int & abs(x1)<1)) # TRUE
	
	     x2 <- pi*100^(-1:3)
	     round(x2, 3)
	     signif(x2, 3)