+--------------+-------------------+
| warpbreaks   | 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)

