#' @title Fitting IDF model parameters to annual maximum intensity time series
#' @description The function \code{IDF.short} fits the IDF model parameters \code{mu,sigma,xi,eta,theta}
#' to vectors of annnual maximum intensities \code{int.vec} at different durations \code{durs}.
#' The starting values of the IDF model parameters can be determined by the user as well as specific options to use
#' during optimization. Logartihmic transformation, debugging, the optimization method, and an option to plot the
#' IDF curves.
#' @param ints.vec a \code{vector} of yearly maxima of intensity sorted by year and aggregatin level
#' @param durs a vector of aggregation levels used to fit the IDF curves. One value for each year. Has to have same lenght as \code{int.vec}
#' @param n.y \code{integer} value specifying the number of years of data
#' @param mu.init initial estimation of location parameter, default is NA. Initial value estimated by fitting individual gev parameters
#' @param sigma.init initial estimation of scale parameter,default is NA. Initial value estimated by fitting individual gev parameters
#' @param xi.init inital estimation of shape parameter, default is NA. Initial value estimated by fitting individual gev parameters
#' @param eta.init intial estimation of slope parameter for sigma-power law, default is NA. Initial value estimated by fitting individual gev parameters
#' @param theta.init inital value defining the curvature of the IDF, default is zero, it is not recommended to change it
#' @param use.log \code{logical} value for usage of logarithmic values, default is \code{FALSE}
#' @param DEBUG \code{logical} value for usage of debugging, if \code{TRUE} the input parameters and the value of negative
# 'log-likelihood are printed on console for each iteration during optimization.
#' @param method \code{character} defining the method to be used in \code{optim}, preferences are: "Nelder-Mead", "BFGS", "L-BFGS-B"e
#' @param lower \code{vector} specifying the lower boundary of parameters for "L-BFGS-B" method
#' @param upper \code{vector} specifying the upper boundary of parameters for "L-BFGS-B" method
#' @param plot \code{logical} option of creating a plot of IDF curves with estimated parameters.
#' @param probs a vector of probabilities for which the IDF curves are calculated
#' @param cols a vector of colors for the seperate IDF curves, needs same length as \code{probs}
#' @param station.name \code{character} overall naming of the IDF plot, e.g. name of location or model name
#' @param data.name \code{character} naming the data points, e.g. obs or model name
#' @return $ints vector of sorted intensities for selected aggregation levels
#' @return $durs vector of sorted aggregation levels
#' @return $min minimum value of negative log-likelihood during optimization
#' @return $par vector of estimated IDF model parameters mu,sigma,xi,theta,eta at minimum value of negative log-likelihood.