data(ganglia)"ppp"
representing the point pattern of cell locations.
Entries include
x Cartesian $x$-coordinate of cell
y Cartesian $y$-coordinate of cell
marks factor with levels off and on
indicating ``off'' and ``on'' cells
}
See ppp.object for details of the format.The pattern was first analysed by W"assle et al (1981) using nearest neighbour distances. The data used in their analysis are not available.
The present dataset ganglia was
scanned from Figure 6(a) of W"assle et al (1981)
in the early 1990's, but we have no further information.
This dataset is the one analysed by Van Lieshout and Baddeley (1999)
using multitype J functions, and by Stoyan (1995) using second
order methods (pair correlation and mark correlation).
It has now been discovered that these data are incorrect.
They are not faithful to the scale in Figure 6 of W"assle et al (1981),
and they contain some scanning errors.
Hence they should not be used to address the original scientific question.
They have been retained only for comparison with other analyses
in the statistical literature.
A new, corrected dataset, scanned from the original microscope image,
has been provided under the name betacells. Use that
dataset for any further study.
betacells.W"assle, H., Boycott, B. B. & Illing, R.-B. (1981). Morphology and mosaic of on- and off-beta cells in the cat retina and some functional considerations. Proc. Roy. Soc. London Ser. B 212, 177--195.