localgaussSpec: localgaussSpec

localgaussSpecR Documentation

localgaussSpec

Description

A package for the investigation of univariate and multivariate time series by means of Local Gaussian (auto- and cross-) correlations, and the corresponding spectral densities.

Overview

The localgaussSpec-package investigates strictly stationary time series by the help of a local Gaussian approach. This implies that local Gaussian auto- and cross-correlations are computed for a selection of lags and a selection of points – and based on this it is then possible to investigate the corresponding (m-truncated) local Gaussian spectra. The local Gaussian correlation coincides with the ordinary correlation when a Gaussian structure is investigated, which implies that it is of interest to compare the ordinary spectra and the local Gaussian spectra since that can reveal the presence of non-Gaussian dependency structures in the time series under investigation.

The scripts for reproducibility of results

The scripts that are included in this package provide a simple way to see how the different key-functions should be put together in order to investigate both simulated and real examples. These scripts are included in order to allow interested readers to reproduce the results and figures in the papers based on this local Gaussian approach, but they can easily be modified in order to investigate similar investigations for other cases.

Workflow for simulated time series

The scripts for the simulated time series are based on the following sequence of steps and key functions. The localgaussSpec package must be loaded, and a main_dir-argument must be specified. The function TS_sample is then called in order to create the desired collection of samples, and this is done by the help of a TS_key-argument and parameters suitable for this particular key. The required generating functions is part of an internal list called TS_family, and this list can be extended on demand. Based on the generated time series, a unique save_dir is computed, and the function TS_LG_object is then used to initiate a file-hierarchy, in which the results of the local Gaussian investigation will be stored. The next step is then to specify some details related to the tuning parameters for the estimation algorithm, and for this part the function LG_select_points can be used to specify different configurations of the points to be investigated (e.g. points along the diagonal or points in a rectangular grid). After this, the scribe-function LG_approx_scribe is called in order to perform assorted tasks related to the computation, including a simple check that can prevent previously computed tasks to be recomputed. If a new computation is encountered, then the scribe-function will save the resulting data into the file hierarchy. The scribe will return a main_dir-argument and a data_dir-argument, which is needed in order for LG_shiny to start a shiny-application that enables an interactive inspection of the resulting local Gaussian auto- and cross-correlations, together with different graphical visualisations of the corresponding local Gaussian spectra.

Workflow for real data

The scripts for the real samples are quite similar to those described for the simulated time series. An obvious difference is that TS_sample should not be used, since a sample after all is present. This real sample is sent into TS_LG_object, which creates a unique save_dir based on the given observations. After this the same procedure is applied with regard to selecting the tuning parameters for the local Gaussian estimation, and LG_approx_scribe is used on the single sample. After this, the function LG_boot_approx_scribe can be used to produce resampled versions of the time series, and based on the local Gaussian estimates from these resampled versions it is then possible to obtain pointwise confidence intervals for the estimates based on the original sample. This scribe-function will also return a main_dir-argument and a data_dir-argument, in order for the LG_shiny-function to start the interactive shiny-investigation.


LAJordanger/localgaussSpec documentation built on May 6, 2023, 4:31 a.m.