An object of this class is a convenient way of storing
(and later plotting, editing, etc)
a set of functions \(f_{i,j}(r)\) of a real argument \(r\),
defined for each possible pair \((i,j)\) of indices
\(1 \le i,j \le n\). We may think of this
as a matrix or array of functions \(f_{i,j}\).

Function arrays are particularly useful in the
analysis of a multitype point pattern (a point pattern in which
the points are identified as belonging to separate types).
We may want to compute a summary function for the points
of type \(i\) only, for each of the possible types \(i\).
This produces a \(1 \times m\) array of functions.
Alternatively we may compute a summary function
for each possible pair of types \((i,j)\).
This produces an \(m \times m\) array of functions.

For multitype point patterns the command `alltypes`

will compute arrays of summary functions for each possible
type or for each possible pair of types.
The function `alltypes`

returns an object of class `"fasp"`

.

An object of class `"fasp"`

is a list containing at least the
following components:

- fns
A list of data frames, each representing one of the functions.

- which
A matrix representing the spatial arrangement of the
functions. If `which[i,j] = k`

then the function represented by `fns[[k]]`

should be plotted
in the panel at position \((i,j)\). If `which[i,j] = NA`

then nothing is plotted in that position.

- titles
A list of character strings, providing suitable plotting titles
for the functions.

- default.formulae
A list of default formulae for plotting each of the functions.

- title
A character string, giving a default title for the array
when it is plotted.