warpbreaks             package:datasets             R Documentation

_T_h_e _N_u_m_b_e_r _o_f _B_r_e_a_k_s _i_n _Y_a_r_n _d_u_r_i_n_g _W_e_a_v_i_n_g

_D_e_s_c_r_i_p_t_i_o_n:

     This data set gives the number of warp breaks per loom, where a
     loom corresponds to a fixed length of yarn.

_U_s_a_g_e:

     warpbreaks

_F_o_r_m_a_t:

     A data frame with 54 observations on 3 variables.

       '[,1]'  'breaks'   numeric  The number of breaks
       '[,2]'  'wool'     factor   The type of wool (A or B)
       '[,3]'  'tension'  factor   The level of tension (L, M, H)

     There are measurements on 9 looms for each of the six types of
     warp ('AL', 'AM', 'AH', 'BL', 'BM', 'BH').

_S_o_u_r_c_e:

     Tippett, L. H. C. (1950) _Technological Applications of
     Statistics_. Wiley.  Page 106.

_R_e_f_e_r_e_n_c_e_s:

     Tukey, J. W. (1977) _Exploratory Data Analysis_. Addison-Wesley.

     McNeil, D. R. (1977) _Interactive Data Analysis_. Wiley.

_S_e_e _A_l_s_o:

     'xtabs' for ways to display these data as a table.

_E_x_a_m_p_l_e_s:

     require(stats); require(graphics)
     summary(warpbreaks)
     opar <- par(mfrow = c(1,2), oma = c(0, 0, 1.1, 0))
     plot(breaks ~ tension, data = warpbreaks, col = "lightgray",
          varwidth = TRUE, subset = wool == "A", main = "Wool A")
     plot(breaks ~ tension, data = warpbreaks, col = "lightgray",
          varwidth = TRUE, subset = wool == "B", main = "Wool B")
     mtext("warpbreaks data", side = 3, outer = TRUE)
     par(opar)
     summary(fm1 <- lm(breaks ~ wool*tension, data = warpbreaks))
     anova(fm1)