R: Create, test for and print affine matrices

isAffine {RNiftyReg} | R Documentation

## Create, test for and print affine matrices

### Description

`isAffine` returns a logical value indicating whether its argument is, or resembles, a 4x4 affine matrix. `asAffine` converts a suitable matrix to the affine class, attaching the source and target images as attributes. Affine transformations are a class of linear transformations which preserve points, straight lines and planes, and may consist of a combination of rotation, translation, scale and skew operations.

### Usage

    isAffine(object, strict = FALSE)

    asAffine(object, source = NULL, target = NULL)

    ## S3 method for class 'affine'
    print(x, ...)

### Arguments

`object` | An R object.
`strict` | If `TRUE`, this function just tests whether the object is of class `"affine"`. Otherwise it also tests for an affine-like 4x4 matrix.
`source, target` | Source and target images for the transformation.
`x` | An `"affine"` object.
`...` | Additional parameters to methods. Currently unused.

### Details

NiftyReg's convention is for affine matrices to transform world coordinates (in the sense of `voxelToWorld`) from TARGET to SOURCE space, although transforms are logically applied the other way.

### Value

A logical value, which is `TRUE` if `object` appears to be an affine matrix.

### Note

2D affines are a subset of 3D affines, and are stored in a 4x4 matrix for internal consistency, even though a 3x3 matrix would suffice.

### Author(s)

Jon Clayden <code@clayden.org>

[Package RNiftyReg version 2.7.0 Index]