Momocs (version 1.0.0)

coeff_sel: Helps to select a given number of harmonics from a numerical vector.

Description

coeff_sel helps to select a given number of harmonics by returning their indices when arranged as a numeric vector. For instance, harmonic coefficients are arranged in the $coe slot of Coe-objects in that way: $A_1, \dots, A_n, B_1, \dots, B_n, C_1, \dots, C_n, D_1, \dots, D-n$ after an elliptical Fourier analysis (see efourier and efourier) while $C_n and D_n$ harmonic are absent for radii variation and tangent angle approaches (see rfourier and tfourier respectively). . This function is used internally but might be of interest elwewhere.

Usage

coeff_sel(retain = 8, drop = 0, nb.h = 32, cph = 4)

Arguments

retain

numeric. The number of harmonics to retain.

drop

numeric. The number of harmonics to drop

nb.h

numeric. The maximum harmonic rank.

cph

numeric. Must be set to 2 for rfourier and tfourier were used.

Value

coeff_sel returns indices that can be used to select columns from an harmonic coefficient matrix. coeff_split returns a named list of coordinates.

Examples

data(bot)
bot.f <- efourier(bot, 32)
coe <- bot.f$coe # the raw matrix
coe
# if you want, say the first 8 harmonics but not the first one
retain <- coeff_sel(retain=8, drop=1, nb.h=32, cph=4)
head(coe[, retain])