tfourier_i: Inverse tangent angle Fourier transform

In Momocs: Morphometrics using R

Inverse tangent angle Fourier transform

Description

tfourier_i uses the inverse tangent angle Fourier transformation to calculate a shape, when given a list with Fourier coefficients, typically obtained computed with tfourier.

Usage

tfourier_i(
  tf,
  nb.h,
  nb.pts = 120,
  force2close = FALSE,
  rescale = TRUE,
  perim = 2 * pi,
  thetao = 0
)

Arguments

tf	a list with ao, an and bn components, typically as returned by tfourier
nb.h	integer. The number of harmonics to calculate/use
nb.pts	integer. The number of points to calculate
force2close	logical. Whether to force the outlines calculated to close (see coo_force2close).
rescale	logical. Whether to rescale the points calculated so that their perimeter equals perim.
perim	The perimeter length to rescale shapes.
thetao	numeric. Radius angle to the reference (in radians)

Details

See tfourier for the mathematical background.

Value

A list with components:

x	vector of x-coordinates.
y	vector of y-coordinates.
phi	vector of interpolated changes on the tangent angle.
angle	vector of position on the perimeter (in radians).

Note

Directly borrowed for Claude (2008), and called ifourier2 there.

References

Zahn CT, Roskies RZ. 1972. Fourier Descriptors for Plane Closed Curves. IEEE Transactions on Computers C-21: 269-281.

Claude, J. (2008) Morphometrics with R, Use R! series, Springer 316 pp.

See Also

Other tfourier: tfourier_shape(), tfourier()

Examples

tfourier(bot[1], 24)
tfourier_shape()

Momocs documentation built on Nov. 13, 2023, 5:07 p.m.