+------------+-------------------+
| faithful   | R Documentation   |
+------------+-------------------+

Old Faithful Geyser Data
------------------------

Description
~~~~~~~~~~~

Waiting time between eruptions and the duration of the eruption for the
Old Faithful geyser in Yellowstone National Park, Wyoming, USA.

Usage
~~~~~

::

    faithful

Format
~~~~~~

A data frame with 272 observations on 2 variables.

+--------+-------------+-----------+-------------------------------------------+
| [,1]   | eruptions   | numeric   | Eruption time in mins                     |
+--------+-------------+-----------+-------------------------------------------+
| [,2]   | waiting     | numeric   | Waiting time to next eruption (in mins)   |
+--------+-------------+-----------+-------------------------------------------+
+--------+-------------+-----------+-------------------------------------------+

Details
~~~~~~~

A closer look at ``faithful$eruptions`` reveals that these are heavily
rounded times originally in seconds, where multiples of 5 are more
frequent than expected under non-human measurement. For a better version
of the eruption times, see the example below.

There are many versions of this dataset around: Azzalini and Bowman
(1990) use a more complete version.

Source
~~~~~~

W. Härdle.

References
~~~~~~~~~~

Härdle, W. (1991) *Smoothing Techniques with Implementation in S*. New
York: Springer.

Azzalini, A. and Bowman, A. W. (1990). A look at some data on the Old
Faithful geyser. *Applied Statistics* **39**, 357–365.

See Also
~~~~~~~~

``geyser`` in package `MASS <http://CRAN.R-project.org/package=MASS>`_
for the Azzalini–Bowman version.

Examples
~~~~~~~~

::

    require(stats); require(graphics)
    f.tit <-  "faithful data: Eruptions of Old Faithful"

    ne60 <- round(e60 <- 60 * faithful$eruptions)
    all.equal(e60, ne60)             # relative diff. ~ 1/10000
    table(zapsmall(abs(e60 - ne60))) # 0, 0.02 or 0.04
    faithful$better.eruptions <- ne60 / 60
    te <- table(ne60)
    te[te >= 4]                      # (too) many multiples of 5 !
    plot(names(te), te, type="h", main = f.tit, xlab = "Eruption time (sec)")

    plot(faithful[, -3], main = f.tit,
         xlab = "Eruption time (min)",
         ylab = "Waiting time to next eruption (min)")
    lines(lowess(faithful$eruptions, faithful$waiting, f = 2/3, iter = 3),
          col = "red")

