% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/fs.R
\name{fs}
\alias{fs}
\title{Generation of Fourrier series.}
\usage{
fs(X, nharmonics)
}
\arguments{
\item{X}{must be a dataframe with columns k1,k2,..., . One period is from 0 to 1
(so for example if X is hour of day, then divide X by 24 to obtain a daily period).}

\item{nharmonics}{the number of harmonics, so creates double as many inputs! i.e. one sine and one cos for each harmonic.}
}
\value{
Returns a list of dataframes (two for each i in \code{1:nharmonics}) with same number of columns as X.
}
\description{
Function for generating Fourrier series as a function of x E.g. use for
harmonic functions for modelling the diurnal patterns or for basis functions.
}
\examples{
# Make a data.frame with time of day in hours for different horizons
tday <- make_tday(seq(ct("2019-01-01"), ct("2019-01-04"), by=3600), kseq=1:5)
# See whats in it
str(tday)
head(tday)

# Now use the function to generate Fourier series
L <- fs(tday/24, nharmonics=2)
# See what is in it
str(L)

# Make a plot to see the harmonics
par(mfrow=c(2,1))
# The first harmonic
plot(L$sin1$k1, type="l")
lines(L$cos1$k1, type="l")
# The second harmonic
plot(L$sin2$k1, type="l")
lines(L$cos2$k1, type="l")


}