From jouni.helske at jyu.fi  Mon Mar 16 09:21:19 2015
From: jouni.helske at jyu.fi (Helske, Jouni)
Date: Mon, 16 Mar 2015 08:21:19 +0000
Subject: [Rd] Initial covariance matrix in StructTS
Message-ID: <7FC11B33B8C53E4EB9510C0BAA73EAE34101AE2E@mbs2.ad.jyu.fi>

Dear all,

The definition of the initial covariance matrix P in StructTS function seems to be defined in a somewhat non-standard way without any references. Usually that matrix is defined as a diagonal matrix in case of structural time series models, but StructTS defines this as a singular matrix filled with  1e+06 * var(x, na.rm = TRUE)/100 where x is the time series being modelled.

I wonder if this is a bug or an undocumented feature?

There was more detailed question by Javier L?pez-de-Lacalle in R-help last November without replies:  https://stat.ethz.ch/pipermail/r-help//2014-November/423128.html<https://stat.ethz.ch/pipermail/r-help/2014-November/423128.html>

There is also illustrative figure in his blog post about the effects of this initial covariance matrix (scroll to the bottom of the page):
http://www.jalobe.com:8080/blog/variations-on-a-maximum-likelihood-procedure/

Best regards,

Jouni Helske

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[Rd] Initial covariance matrix in StructTS
Helske, Jouni