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.