#' Add amplitude weights to the zero-weighted frequencies of an existing
#' Fourier descriptor generated by
#' \code{\link{random.fourier.descriptor}}
#'
#' Returns a new Fourier descriptor.
#'
#' @include random-fourier-descriptor.R
#' @param fourier.descriptor A Fourier descriptor object generated by
#' \code{\link{random.fourier.descriptor}}
#' @param new.frequencies How many frequency components should be added?
#' Defaults to 1.
#' @param generating.function An anonymous function that returns an amplitude
#' weight. The default function adds weight 1 to each new frequency.
#' @export
#' @examples
#' fourier.descriptor <- random.fourier.descriptor(12)
#'
#' fd <- complicate.fourier.descriptor(fourier.descriptor)
#'
#' fd <- complicate.fourier.descriptor(fourier.descriptor,
#' generating.fourier = functions() {return(runif(1))})
#' @usage
#' fourier.descriptor <- random.fourier.descriptor(12)
#'
#' fd <- complicate.fourier.descriptor(fourier.descriptor)
complicate.fourier.descriptor <- function(fourier.descriptor,
quantity = 1,
generating.function = function() {return(1)})
{
zero.frequencies <- which(fourier.descriptor[['Amplitude']] == 0)
even.frequencies <- which(1:length(fourier.descriptor[['Amplitude']]) %% 2 == 0)
allowed.frequencies <- intersect(zero.frequencies, even.frequencies)
if (length(allowed.frequencies) < quantity)
{
stop('Not enough frequencies to perform complication')
}
if (length(allowed.frequencies) == 1)
{
add.frequencies <- allowed.frequencies
}
else
{
add.frequencies <- sample(allowed.frequencies, quantity)
}
for (frequency in add.frequencies)
{
fourier.descriptor[['Amplitude']][frequency] <- generating.function()
}
return(fourier.descriptor)
}
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