Momocs (version 0.2-6)

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 @coeff 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

coeff.sel(retain=8, drop=0, nb.h=12)        #efourier 
coeff.sel(retain=8, drop=0, nb.h=12, cph=2) #r/tfourier

# if you want to export the matrix of coefficients but only the first 6 colums.
data(bot)
bot.f <- eFourier(bot, nb.h=12)
bot.f@coe[, coeff.sel(6, 0, 12)]