Sorry, I don't understand your design. I try to show, what/how I best
understand and what questions are open:


Ronald Bloom schrieb:
...
> So let's say I have 51 variables.  I collect them 30 days at a time.

I assume the following scheme:

             data of 30 days        data of 30 days           data of 30 days
   var01 !                   !     !                   !     !                   !     
   var02 !                   !     !                   !     !                   !     
   var03 !                   !     !                   !     !                   !     
   ...                       !     !                   !     !                   !     
   var50 !                   !     !                   !     !                   !     
   var51 !                   !     !                   !     !                   !     
         +-------------------+     +-------------------+     +-------------------+
               D1                        D2                        D3 

> 
> Every time I collect a new set of observations I want to assess
> its "surprise value", in respect of the recent past.

... a surprise-value of the whole new set D2 respectively to D1...

> 
> So I have a monthly covariance matrix of rank 30.  There should be
> 30 non-zero eigenvalues.  

    cov01 = D1*D1'/30
    cov02 = D2*D2'/30
    ...


>                           If I get one more observation (of 51 items)

 "one more observation" ????
 ????  a.1) One single observation or
       a.2) a new set of 30 days-observations?

> can I map it into the reduced dimension subspace of size 30,

 ???? b.1) you try to find a composition of D1-days to match your new single 
           observation 
      b.2) you try to match the factor-structure of the new set of observations 
           D2 with that of D1 ?


> and evaluate it for "extremity" using a multivariate prediction
> "region" using the 30x30 diagonal matrix of eigenvalues in
> the standard "hotelling form" on the reduced space?

      b.3) you try to match the new eigenvalue-structures of D2 to the
           old of D1 ??

> 
> I'm just trying to translate theory into something I can
> actually practise.
> 

Gottfried Helms

--
Gottfried Helms
Univ. Kassel
.
.
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