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.Beta cells are associated with the resolution of fine detail in the cat's visual system. They can be classified anatomically as ``on'' or ``off''. Statistical independence of the ``on''- and ``off''-components would strengthen the claim that there are two separate channels for ``brightness'' and ``darkness'' as postulated by Hering in 1874. For details see Waessle et al (1981).
These data have been analysed by Diggle (1986) and Van Lieshout and Baddeley (1999).
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.