create.pgrid {ExceedanceTools}

Create grid of locations.

Description

create.pgrid creates a grid of locations from the boundaries of domain and other information.

Usage

create.pgrid(
  xmin,
  xmax,
  ymin,
  ymax,
  nx,
  ny,
  midpoints = FALSE,
  poly.coords = NULL
)

Arguments

xmin

The minimum value of the boundary of the x coordinates of the spatial domain.

xmax

The maximum value of the boundary of the x coordinates of the spatial domain.

ymin

The minimum value of the boundary of the y coordinates of the spatial domain.

ymax

The maximum value of the boundary of the y coordinates of the spatial domain.

nx

The number of gridpoints/cells/pixels in the x direction.

ny

The number of gridpoints/cells/pixels in the y direction.

midpoints

A logical value (TRUE or FALSE) indicating whether the boundary values are for the midpoint of a pixel (midpoints = TRUE) or for the boundary of the spatial domain in general (midpoints = FALSE), in which case the midpoints are calculated internally). Default is FALSE.

poly.coords

An n \times 2 matrix with the coordinates specifying the polygon vertices of the true spatial domain of interest within the rectangular boundaries provided by xmin, xmax, ymin, and ymax. If this is provided, the pgrid returned will be within the convex hull of poly.coords.

Details

The key argument in the function midpoints. If this is TRUE, it is assumed that the boundaries of the spatial domain correspond to the midpoints of the cell/pixel in the grid. Otherwise, it is assumed that the boundaries correspond to the actual borders of the region of interest. If poly.coords is supplied, the grid returned is the grid of midpoints contained in the convex hull of poly.coords.

Value

Returns an object of class pgrid with the following components:

pgrid

An n \times 2 matrix of locations (the midpoints of the pixelized grid).

m

The number of rows in pgrid.

p.in.grid

A vector of 0s and 1s indicating whether the midpoint of each pixel is in the convex hull of poly.coords. If poly.coords is not provided, this is a vector of 1s.

ubx

The pixel boundaries in the x direction.

uby

The pixel boundaries in the y direction.

upx

The pixel midpoints in the x direction.

upy

The pixel midpoints in the y direction.

Author(s)

Joshua French

Examples

pgrida <- create.pgrid(0, 1, 0, 1, nx = 50, ny = 50, midpoints = FALSE)
pgridb <- create.pgrid(.01, .99, .01, .99, nx = 50, ny = 50, midpoints = TRUE)