freesurferformats (version 1.1.0)

invert.fs.transform: Invert a transformation.

Description

Compute the transformation that undoes the given one, i.e. the one that maps the target coordinates back to the source coordinates. The source and target of the result are swapped, along with the coordinate spaces, and the matrix is inverted. A transformation is never stored inverted, use this function when you need the reverse mapping.

Usage

invert.fs.transform(tf)

Value

an fs.transform instance that maps from the target of tf back to its source.

Arguments

tf

an fs.transform instance.

See Also

Other header coordinate space: is.fs.transform(), mghheader.is.ras.valid(), mghheader.ras2vox(), mghheader.ras2vox.tkreg(), mghheader.scanner2tkreg(), mghheader.tkreg2scanner(), mghheader.vox2ras(), mghheader.vox2ras.tkreg(), print.fs.transform(), read.fs.transform(), read.fs.transform.dat(), read.fs.transform.fslmat(), read.fs.transform.itk(), read.fs.transform.lta(), read.fs.transform.xfm(), sm0to1(), sm1to0(), summary.fs.transform(), transform2lps(), transform2ras(), transform2voxel(), transform2world(), write.fs.transform(), write.fs.transform.dat(), write.fs.transform.fslmat(), write.fs.transform.itk(), write.fs.transform.lta(), write.fs.transform.xfm()

Examples

tf <- read.fs.transform(system.file("extdata", "talairach.xfm",
  package = "freesurferformats", mustWork = TRUE
))
tf_back <- invert.fs.transform(tf)
tf_back$space_in # the spaces are swapped
max(abs(tf_back$matrix %*% tf$matrix - diag(4))) # the identity