spatstat (version 1.23-1)

nearest.raster.point: Find Pixel Nearest to a Given Point

Description

Given cartesian coordinates, find the nearest pixel.

Usage

nearest.raster.point(x,y,w, indices=TRUE)

Arguments

x

Numeric vector of $x$ coordinates of any points

y

Numeric vector of $y$ coordinates of any points

w

A window (an object of class "owin") of type "mask" representing a binary pixel image.

indices

Logical flag indicating whether to return the row and column indices, or the actual $x,y$ coordinates.

Value

• If indices=TRUE, a list containing two vectors rr and cc giving row and column positions (in the image matrix). If indices=FALSE, a list containing vectors x and y giving actual coordinates of the pixels.

Details

The argument w should be a window (an object of class "owin", see owin.object for details) of type "mask". This represents a binary pixel image.

The arguments x and y should be numeric vectors of equal length. They are interpreted as the coordinates of points in space. For each point (x[i], y[i]), the function finds the nearest pixel in the grid of pixels for w.

If indices=TRUE, this function returns a list containing two vectors rr and cc giving row and column positions (in the image matrix). For the location (x[i],y[i]) the nearest pixel is at row rr[i] and column cc[i] of the image.

If indices=FALSE, the function returns a list containing two vectors x and y giving the actual coordinates of the pixels.

See Also

owin.object, as.mask

Examples

w <- owin(c(0,1), c(0,1), mask=matrix(TRUE, 100,100))  # 100 x 100 grid
  nearest.raster.point(0.5, 0.3, w)
  nearest.raster.point(0.5, 0.3, w, indices=FALSE)