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#' Interpolation for iAR, CiAR, and BiAR Classes
#'
#' Performs interpolation on time series with missing values. This method is implemented for:
#' 1. Irregular Autoregressive models (iAR)
#' 2. Complex Irregular Autoregressive models (CiAR)
#' 3. Bivariate Autoregressive models (BiAR)
#'
#' @name interpolation
#'
#' @param x An object of class \code{iAR}, \code{CiAR}, or \code{BiAR}, containing the model specification and parameters:
#' \itemize{
#' \item For \code{iAR}:
#' \itemize{
#' \item \code{family}: The distribution family of the iAR model (one of "norm", "t", or "gamma").
#' \item \code{series}: A numeric vector representing the time series to interpolate.
#' \item \code{coef}: The coefficients of the iAR model.
#' \item \code{zero_mean}: Logical, whether the model assumes a zero-mean series.
#' \item \code{standardized}: Logical, whether the model uses standardized data (only for "norm" family).
#' \item \code{mean}: The mean parameter (only for "gamma" family).
#' }
#' \item For \code{CiAR}:
#' \itemize{
#' \item \code{coef}: The coefficients of the CiAR model.
#' \item \code{series_esd}: The series of error standard deviations for the CiAR model.
#' \item \code{zero_mean}: Logical, whether the model assumes a zero-mean series.
#' \item \code{standardized}: Logical, whether the model uses standardized data.
#' \item \code{seed}: Optional seed for random number generation.
#' }
#' \item For \code{BiAR}:
#' \itemize{
#' \item \code{coef}: The coefficients of the BiAR model.
#' \item \code{series_esd}: The series of error standard deviations for the BiAR model.
#' \item \code{zero_mean}: Logical, whether the model assumes a zero-mean series.
#' \item \code{yini1}: Initial value for the first time series (for BiAR models).
#' \item \code{yini2}: Initial value for the second time series (for BiAR models).
#' \item \code{seed}: Optional seed for random number generation.
#' }
#' }
#'
#' @param ... Additional arguments (unused).
#'
#' @return An object of the same class as \code{x} with interpolated time series.
#'
#' @description
#' This method performs imputation of missing values in a time series using an autoregressive model.
#' The imputation is done iteratively for each missing value, utilizing available data and model coefficients.
#' Depending on the model family, the interpolation is performed differently:
#' - For \code{norm}: A standard autoregressive model for normally distributed data.
#' - For \code{t}: A model for time series with t-distributed errors.
#' - For \code{gamma}: A model for time series with gamma-distributed errors.
#' - For \code{CiAR}: A complex irregular autoregressive model.
#' - For \code{BiAR}: A bivariate autoregressive model.
#'
#' @details
#' The method handles missing values (NA) in the time series by imputing them iteratively.
#' For each missing value, the available data is used to fit the autoregressive model, and the missing value is imputed based on the model's output.
#' For the \code{CiAR} and \code{BiAR} models, the error standard deviations and initial values are also considered during imputation.
#'
#' @seealso \code{\link{forecast}} for forecasting methods for these models.
#'
#' @references
#' \insertRef{Eyheramendy_2018}{iAR},\insertRef{Elorrieta_2019}{iAR},\insertRef{Elorrieta_2021}{iAR}
#'
#' @examples
#' # Interpolation for iAR model
#' library(iAR)
#' n=100
#' set.seed(6714)
#' o=iAR::utilities()
#' o<-gentime(o, n=n)
#' times=o@times
#' model_norm <- iAR(family = "norm", times = times, coef = 0.9)
#' model_norm <- sim(model_norm)
#' y=model_norm@series
#' y1=y/sd(y)
#' model_norm@series=y1
#' model_norm@series_esd=rep(0,n)
#' model_norm <- kalman(model_norm)
#' print(model_norm@coef)
#' napos=10
#' model_norm@series[napos]=NA
#' model_norm <- interpolation(model_norm)
#' interpolation=na.omit(model_norm@interpolated_values)
#' mse=as.numeric(y1[napos]-interpolation)^2
#' print(mse)
#' plot(times,y,type='l',xlim=c(times[napos-5],times[napos+5]))
#' points(times,y,pch=20)
#' points(times[napos],interpolation*sd(y),col="red",pch=20)
#'
#' # Interpolation for CiAR model
#' model_CiAR <- CiAR(times = times,coef = c(0.9, 0))
#' model_CiAR <- sim(model_CiAR)
#' y=model_CiAR@series
#' y1=y/sd(y)
#' model_CiAR@series=y1
#' model_CiAR@series_esd=rep(0,n)
#' model_CiAR <- kalman(model_CiAR)
#' print(model_CiAR@coef)
#' napos=10
#' model_CiAR@series[napos]=NA
#' model_CiAR <- interpolation(model_CiAR)
#' interpolation=na.omit(model_CiAR@interpolated_values)
#' mse=as.numeric(y1[napos]-interpolation)^2
#' print(mse)
#' plot(times,y,type='l',xlim=c(times[napos-5],times[napos+5]))
#' points(times,y,pch=20)
#' points(times[napos],interpolation*sd(y),col="red",pch=20)
#' # Interpolation for BiAR model
#' model_BiAR <- BiAR(times = times,coef = c(0.9, 0.3), rho = 0.9)
#' model_BiAR <- sim(model_BiAR)
#' y=model_BiAR@series
#' y1=y/apply(y,2,sd)
#' model_BiAR@series=y1
#' model_BiAR@series_esd=matrix(0,n,2)
#' model_BiAR <- kalman(model_BiAR)
#' print(model_BiAR@coef)
#' napos=10
#' model_BiAR@series[napos,1]=NA
#' model_BiAR <- interpolation(model_BiAR)
#' interpolation=na.omit(model_BiAR@interpolated_values[,1])
#' mse=as.numeric(y1[napos,1]-interpolation)^2
#' print(mse)
#' par(mfrow=c(2,1))
#' plot(times,y[,1],type='l',xlim=c(times[napos-5],times[napos+5]))
#' points(times,y[,1],pch=20)
#' points(times[napos],interpolation*apply(y,1,sd)[1],col="red",pch=20)
#' plot(times,y[,2],type='l',xlim=c(times[napos-5],times[napos+5]))
#' points(times,y[,2],pch=20)
#' @export
interpolation <- S7::new_generic("interpolation", "x")
S7::method(generic = interpolation, signature = iAR) <- function(x, yini = 0) {
if(length(x@series)==0) stop("The interpolation method needs a time series")
if(x@family == "norm"){
if(length(x@coef)==0) stop("The interpolation method needs the coefficient of the iAR model")
# Original series
vector <- x@series
# Find positions of NA values in the vector
nas <- which(is.na(vector))
# If there are NA values, return the imputed vector
if (length(nas) > 0) {
for (i in seq_along(nas)) {
# Current position of NA value
na_pos <- nas[i]
# Data available up to before the current NA value
if((i+1) <= length(nas)){
available_data <- vector[-nas[((i+1):length(nas))]]
available_times <- x@times[-nas[((i+1):length(nas))]]
} else {
available_data <- vector
available_times <- x@times
}
if(is.integer(x@series_esd)){
available_series_esd <- x@series_esd
} else {
if((i+1) <= length(nas)) available_series_esd <- x@series_esd[-nas[((i+1):length(nas))]] else available_series_esd <- x@series_esd
}
# Apply the imputation function to the available data
imputed_value <- iARinterpolation(coef = x@coef,
series = available_data,
times = available_times,
series_esd = available_series_esd,
yini = yini,
zero_mean = x@zero_mean,
standardized = x@standardized)$fitted
# Replace the NA value with the imputed value
vector[na_pos] <- imputed_value
}
x@interpolated_values <- vector[nas]
x@interpolated_times <- x@times[nas]
x@interpolated_series <- vector
}
return(x)
}
if(x@family == "t"){
if(length(x@coef)==0) stop("The interpolation method needs the coefficient of the iAR-T model")
# Original series
vector <- x@series
# Find positions of NA values in the vector
nas <- which(is.na(vector))
# If there are NA values, return the imputed vector
if (length(nas) > 0) {
# Iterate over the positions of NA values
for (i in seq_along(nas)) {
# Current position of NA value
na_pos <- nas[i]
# Data available up to before the current NA value
if((i+1) <= length(nas)){
available_data <- vector[-nas[((i+1):length(nas))]]
available_times <- x@times[-nas[((i+1):length(nas))]]
} else {
available_data <- vector
available_times <- x@times
}
if(is.integer(x@series_esd)){
available_series_esd <- x@series_esd
} else {
if((i+1) <= length(nas)) available_series_esd <- x@series_esd[-nas[((i+1):length(nas))]] else available_series_esd <- x@series_esd
}
# Apply the imputation function to the available data
imputed_value <- iARtinterpolation(coef = c(x@coef,x@sigma),
series = available_data,
times = available_times,
df = x@df,
# series_esd = available_series_esd, # es necesario aqui?
# zero_mean = x@zero_mean, # no esta en la funcion original
yini = yini)$fitted
# Replace the NA value with the imputed value
vector[na_pos] <- imputed_value
}
x@interpolated_values <- vector[nas]
x@interpolated_times <- x@times[nas]
x@interpolated_series <- vector
}
return(x)
}
if(x@family == "gamma"){
if(length(x@coef)==0) stop("The interpolation method needs the coefficients of the iAR-Gamma model")
# Original series
vector <- x@series
# Find positions of NA values in the vector
nas <- which(is.na(vector))
# If there are NA values, return the imputed vector
if (length(nas) > 0) {
# Iterate over the positions of NA values
for (i in seq_along(nas)) {
# Current position of NA value
na_pos <- nas[i]
# Data available up to before the current NA value
if((i+1) <= length(nas)){
available_data <- vector[-nas[((i+1):length(nas))]]
available_times <- x@times[-nas[((i+1):length(nas))]]
} else {
available_data <- vector
available_times <- x@times
}
if(is.integer(x@series_esd)){
available_series_esd <- x@series_esd
} else {
if((i+1) <= length(nas)) available_series_esd <- x@series_esd[-nas[((i+1):length(nas))]] else available_series_esd <- x@series_esd
}
# Apply the imputation function to the available data
imputed_value <- iARginterpolation(coef = c(x@coef, x@mean, x@variance),
series = available_data,
times = available_times,
# series_esd = available_series_esd, # preguntar?
yini = yini)$fitted
# Replace the NA value with the imputed value
vector[na_pos] <- imputed_value
}
x@interpolated_values <- vector[nas]
x@interpolated_times <- x@times[nas]
x@interpolated_series <- vector
}
return(x)
}
}
method(interpolation, CiAR) <- function(x, yini = 0, seed = NULL) {
if(length(x@series)==0) stop("The interpolation method needs a time series")
if(length(x@coef)==0) stop("The interpolation method needs the coefficients of the CiAR model")
# Original series
vector <- x@series
# Find positions of NA values in the vector
nas <- which(is.na(vector))
# If there are NA values, return the imputed vector
if (length(nas) > 0) {
# Iterate over the positions of NA values
for (i in seq_along(nas)) {
# Current position of NA value
na_pos <- nas[i]
# Data available up to before the current NA value
if((i+1) <= length(nas)){
available_data <- vector[-nas[((i+1):length(nas))]]
available_times <- x@times[-nas[((i+1):length(nas))]]
} else{
available_data <- vector
available_times <- x@times
}
if(is.integer(x@series_esd)){
available_series_esd <- x@series_esd
} else {
if((i+1) <= length(nas)) available_series_esd <- x@series_esd[-nas[((i+1):length(nas))]] else available_series_esd <- x@series_esd
}
# Apply the imputation function to the available data
imputed_value <- CiARinterpolation(coef = x@coef,
series = available_data,
times = available_times,
series_esd = available_series_esd,
yini = yini,
zero_mean = x@zero_mean,
standardized = x@standardized,
seed = seed)$fitted
# Replace the NA value with the imputed value
vector[na_pos] <- imputed_value
}
x@interpolated_values <- vector[nas]
x@interpolated_times <- x@times[nas]
x@interpolated_series <- vector
}
return(x)
}
method(interpolation, BiAR) <- function(x, yini1 = 0, yini2 = 0, seed = NULL) {
if(length(x@series)==0) stop("The interpolation method needs a bivariate time series")
if(length(x@coef)==0) stop("The interpolation method needs the coefficients of the BiAR model")
# Original series
vector <- x@series
# Find positions of NA values in the vector
nas <- sort(unique(unlist(apply(is.na(vector),2,which))))
auxtimes <- matrix(NA,dim(vector)[1],dim(vector)[2])
auxseries <- auxtimes
# If there are NA values, return the imputed vector
if (length(nas) > 0) {
# Iterate over the positions of NA values
for (i in seq_along(nas)) {
# Current position of NA value
na_pos <- nas[i]
# Data available up to before the current NA value
if((i+1) <= length(nas)){
available_data <- vector[-nas[((i+1):length(nas))],]
available_times <- x@times[-nas[((i+1):length(nas))]]
} else{
available_data <- vector
available_times <- x@times
}
na_serie=which(is.na(available_data[na_pos,]))
nmiss=length(na_serie)
if(is.integer(x@series_esd)) x@series_esd <- matrix(0, nrow=length(x@times),ncol = 2)
if(is.integer(x@series_esd)){
available_series_esd <- x@series_esd
}
else {
x@series_esd[na_pos,na_serie] <- 0
if((i+1) <= length(nas)) available_series_esd <- x@series_esd[-nas[((i+1):length(nas))],] else available_series_esd <- x@series_esd
}
imputed_value <- iAR:::BiARinterpolation(coef = x@coef,
series1 = available_data[,1],
series2 = available_data[,2],
times = available_times,
series_esd1 = available_series_esd[,1],
series_esd2 = available_series_esd[,2],
yini1 = yini1,
yini2 = yini2,
zero_mean = x@zero_mean,nmiss=nmiss)$fitted
# Replace the NA value with the imputed value
vector[na_pos,na_serie] <- imputed_value
auxtimes[na_pos,na_serie] <- x@times[na_pos]
auxseries[na_pos,na_serie] <- vector[na_pos,na_serie]
}
x@interpolated_values <- auxseries
x@interpolated_times <- auxtimes
x@interpolated_series <- vector
}
return(x)
}
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