
96 Spatial Point Patterns: Methodology and Applications with R
gument panel (or upper.panel and lower.panel). The argument sh ould be a function, as de-
scribed in the help f or pairs.default. In spatstat we provide panel functions panel.contour,
panel.image whic h draw con tour maps and image displays, respectively. It is also possible to fill
the diagonal panels with an other plot specified by the argument diag.plot: spatstat provides
the panel function panel.histogram to draw a histogr a m of the p ixel values.
The return value of pairs.im is a data frame containing the corresponding pixel values for
each of the images. This is useful for calculating ...