dfourier_i {Momocs}

Investe discrete cosinus transform

Description

Calculates inverse discrete cosine transforms (see dfourier), given a list of A and B harmonic coefficients, typically such as those produced by dfourier.

Usage

dfourier_i(df, nb.h, nb.pts = 60)

Arguments

df

a list with $A and $B components, containing harmonic coefficients.

nb.h

a custom number of harmonics to use

nb.pts

numeric the number of pts for the shape reconstruction

Value

a matrix of (x; y) coordinates

Note

Only the core functions so far. Will be implemented as an Opn method soon.

References

• Dommergues, C. H., Dommergues, J.-L., & Verrecchia, E. P. (2007). The Discrete Cosine Transform, a Fourier-related Method for Morphometric Analysis of Open Contours. Mathematical Geology, 39(8), 749-763. doi:10.1007/s11004-007-9124-6

• Many thanks to Remi Laffont for the translation in R).

See Also

Other dfourier: dfourier_shape(), dfourier()

Examples

# dfourier and inverse dfourier
o <- olea[1]
o <- coo_bookstein(o)
coo_plot(o)
o.dfourier <- dfourier(o, nb.h=12)
o.dfourier
o.i <- dfourier_i(o.dfourier)
o.i <- coo_bookstein(o.i)
coo_draw(o.i, border='red')

o <- olea[1]
h.range <- 2:13
coo <- list()
for (i in seq(along=h.range)){
coo[[i]] <- dfourier_i(dfourier(o, nb.h=h.range[i]))}
names(coo) <- paste0('h', h.range)
panel(Opn(coo), borders=col_india(12), names=TRUE)
title('Discrete Cosine Transforms')