affine {spatstat}R Documentation

Apply Affine Transformation

Description

Applies any affine transformation of the plane (linear transformation plus vector shift) to a plane geometrical object, such as a point pattern or a window.

Usage

 affine(X, mat=diag(c(1,1)), vec=c(0,0))

Arguments

X Any suitable dataset representing a two-dimensional object, such as a point pattern (object of class "ppp"), or a window (object of class "owin").
mat Matrix representing a linear transformation.
vec Vector of length 2 representing a translation.

Details

This is generic. Methods are provided for point patterns (affine.ppp) and windows (affine.owin).

First the linear transformation represented by mat is applied (multiplying on the left by mat), and then the result is translated by the vector vec.

The argument mat must be a nonsingular 2 * 2 matrix.

Value

Another object of the same type, representing the result of applying the affine transformation.

Author(s)

Adrian Baddeley adrian@maths.uwa.edu.au http://www.maths.uwa.edu.au/~adrian/ and Rolf Turner rolf@math.unb.ca http://www.math.unb.ca/~rolf

See Also

affine.ppp, affine.owin, rotate, shift

Examples

  library(spatstat)
  data(cells)
  # shear transformation
  X <- affine(cells, matrix(c(1,0,0.6,1),ncol=2))
  
  plot(X)
  # rescale y coordinates by factor 1.3
  plot(affine(cells, diag(c(1,1.3))))
  

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