rfourier_shape: Calculates and draw 'rfourier' shapes.

In Momocs: Morphometrics using R

Calculates and draw 'rfourier' shapes.

Description

rfourier_shape calculates a 'Fourier radii variation shape' given Fourier coefficients (see Details) or can generate some 'rfourier' shapes.

Usage

rfourier_shape(an, bn, nb.h, nb.pts = 80, alpha = 2, plot = TRUE)

Arguments

an	numeric. The a_n Fourier coefficients on which to calculate a shape.
bn	numeric. The b_n Fourier coefficients on which to calculate a shape.
nb.h	integer. The number of harmonics to use.
nb.pts	integer. The number of points to calculate.
alpha	numeric. The power coefficient associated with the (usually decreasing) amplitude of the Fourier coefficients (see Details).
plot	logical. Whether to plot or not the shape.

Details

rfourier_shape can be used by specifying nb.h and alpha. The coefficients are then sampled in an uniform distribution (-\pi ; \pi) and this amplitude is then divided by harmonicrank^alpha. If alpha is lower than 1, consecutive coefficients will thus increase. See rfourier for the mathematical background.

Value

A matrix of (x; y) coordinates.

References

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

See Also

Other rfourier: rfourier_i(), rfourier()

Examples

data(bot)
rf <- rfourier(bot[1], 24)
rfourier_shape(rf$an, rf$bn) # equivalent to rfourier_i(rf)
rfourier_shape() # not very interesting

rfourier_shape(nb.h=12) # better
rfourier_shape(nb.h=6, alpha=0.4, nb.pts=500)

# Butterflies of the vignette' cover
panel(Out(a2l(replicate(100,
rfourier_shape(nb.h=6, alpha=0.4, nb.pts=200, plot=FALSE)))))

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