# arma11_to_wv: ARMA(1,1) to WV In SMAC-Group/simts: Time Series Analysis Tools

 arma11_to_wv R Documentation

## ARMA(1,1) to WV

### Description

This function computes the WV (haar) of an Autoregressive Order 1 - Moving Average Order 1 (ARMA(1,1)) process.

### Usage

arma11_to_wv(phi, theta, sigma2, tau)


### Arguments

 phi A double corresponding to the autoregressive term. theta A double corresponding to the moving average term. sigma2 A double the variance of the process. tau A vec containing the scales e.g. 2^{\tau}

### Details

This function is significantly faster than its generalized counter part arma_to_wv

### Value

A vec containing the wavelet variance of the ARMA(1,1) process.

### Process Haar Wavelet Variance Formula

The Autoregressive Order 1 and Moving Average Order 1 (ARMA(1,1)) process has a Haar Wavelet Variance given by:

\nu _j^2\left( {\phi ,\theta ,{\sigma ^2}} \right) = - \frac{{2{\sigma ^2}\left( { - \frac{1}{2}{{(\theta + 1)}^2}\left( {{\phi ^2} - 1} \right){\tau _j} - (\theta + \phi )(\theta \phi + 1)\left( {{\phi ^{{\tau _j}}} - 4{\phi ^{\frac{{{\tau _j}}}{2}}} + 3} \right)} \right)}}{{{{(\phi - 1)}^3}(\phi + 1)\tau _j^2}}

SMAC-Group/simts documentation built on Sept. 4, 2023, 5:25 a.m.