Momocs (version 0.2-6)

tfourier.i: Calculates inverse tangent angle Fourier analysis.

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 = 300, 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)

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).

Details

See tfourier for the mathematical background.

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

tfourier for the reverse operation and also tfourier.shape. l2m, coeff.split may be useful.

Examples

data(bot)
tfourier(bot@coo[[1]], 24)
tfourier.shape()