warpbreaks             package:datasets             R Documentation

The Number of Breaks in Yarn during Weaving

Description:

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

Usage:

     warpbreaks

Format:

     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').

Source:

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

References:

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

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

See Also:

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

Examples:

     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)

