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.