\HeaderA{rock}{Measurements on Petroleum Rock Samples}{rock}
\keyword{datasets}{rock}
\begin{Description}\relax
Measurements on 48 rock samples from a petroleum reservoir.
\end{Description}
\begin{Usage}
\begin{verbatim}rock\end{verbatim}
\end{Usage}
\begin{Format}\relax
A data frame with 48 rows and 4 numeric columns.

\Tabular{rll}{
[,1] & area  & area of pores space, in pixels
out of 256 by 256 \\{}
[,2] & peri  & perimeter in pixels \\{}
[,3] & shape & perimeter/sqrt(area) \\{}
[,4] & perm  & permeability in milli-Darcies
}
\end{Format}
\begin{Details}\relax
Twelve core samples from petroleum reservoirs were sampled by 4
cross-sections.  Each core sample was measured for permeability, and
each cross-section has total area of pores, total perimeter of
pores, and shape.
\end{Details}
\begin{Source}\relax
Data from BP Research, image analysis by Ronit Katz, U. Oxford.
\end{Source}