ar1est: MLE or LSE for AR(1) parameter. Sample mean correction used...
In mleur: Maximum likelihood unit root test

Description Usage Arguments Details Value Author(s) References Examples

Fast exact computation of the MLE for AR(1) by solving the likelihood equation. The sample mean correction is used, so the method is not strickly speaking exact but the name derives from the fact that if the mean is known and was used instead of the sample mean the estimate would be an exact MLE estimate of the parameter in the AR(1) model. It has been shown that effect of estimating the sample mean is negligible.

1	ar1est(z, method = c("MLE", "LSE"))

`z`	time series or vector
`method`	must be "MLE" or "LSE"

The exact MLE for mean-zero an AR(1) time series satisfies a cubic equation. The solution of this equation for the MLE given by Zhang (2002) is used. This approach is more reliable as well as faster than the usual approach to the exact MLE using a numerical optimization technique which can occasionally have convergence problems.

MLE for the parameter

A.I. McLeod and Ying Zhang

Zhang, Y. (2002). Topics in Autoregression, Ph.D. Thesis, University of Western Ontario.

#Example 1
#compare MLE and LSE for vel series
ar1est(vel)
ar1est(vel, method="MLE")
ar1est(vel, method="LSE")
#
#Example 2
ar1est(DiffBA)
ar1est(DiffBA, method="LSE")

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