spatstat (version 1.23-1)

affine.ppp: Apply Affine Transformation To Point Pattern

Description

Applies any affine transformation of the plane (linear transformation plus vector shift) to a point pattern.

Usage

## S3 method for class 'ppp':
affine(X, mat=diag(c(1,1)), vec=c(0,0), ...)

Arguments

X

Point pattern (object of class "ppp").

mat

Matrix representing a linear transformation.

vec

Vector of length 2 representing a translation.

...

Arguments passed to affine.owin affecting the handling of the observation window, if it is a binary pixel mask.

Value

• Another point pattern (of class "ppp") representing the result of applying the affine transformation.

Details

The point pattern, and its window, are subjected first to the linear transformation represented by mat (multiplying on the left by mat), and are then translated by the vector vec. The argument mat must be a nonsingular $2 \times 2$ matrix.

This is a method for the generic function affine.

See Also

affine, affine.owin, rotate, shift

Examples

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))))