This is an s4 class extension of matrix with 7 additional slots.
A worldMatrix object can be viewed as a grid composed of squared patches
(i.e., matrix cells). Patches have two spatial coordinates pxcor and
pycor, representing the location of their center. pxcor and
pycor are always integer and increment by 1. pxcor increases as
you move right and pycor increases as you move up. pxcor and
pycor can be negative if there are patches to the left or below the patch
[pxcor = 0, pycor = 0].
The first four slots of the worldMatrix are: minPxcor, maxPxcor,
minPycor, maxPycor which represent the minimum and maximum patches
coordinates in the worldMatrix.
The slot extent is similar to a Raster* extent. Because pxcor
and pycor represent the spatial location at the center of the patches and the
resolution of them is 1, the extent of the worldMatrix is equal to
xmin = minPxcor - 0.5, xmax = maxPxcor + 0.5, ymin = minPycor - 0.5,
and ymax = maxPycor + 0.5.
The number of patches in a worldMatrix is equal to
((maxPxcor - minPxcor) + 1) * ((maxPycor - minPycor) + 1).
The slot res is equal to 1 as it is the spatial resolution of the patches.
The last slot pCoords is a matrix representing the patches coordinates
of all the matrix cells in the order of cells in a Raster* (i.e., by rows).
Careful: The methods [] and [] <- retrieve or assign values for
the patches in the given order of the patches coordinates provided.
When no patches coordinates are provided, the values retrieved or assigned
is done in the order of the cell numbers as defined in in Raster* objects
(i.e., by rows).
Wilensky, U. 1999. NetLogo. http://ccl.northwestern.edu/netlogo/. Center for Connected Learning and Computer-Based Modeling, Northwestern University. Evanston, IL.