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RE: Octave 3.0


From: Schloegl Alois
Subject: RE: Octave 3.0
Date: Wed, 26 Feb 2003 15:47:56 -0600
User-agent: Internet Messaging Program (IMP) 4.0-cvs


In a recent mail, you ranked 10 features for the next stable release. I'd like 
to comment on two topics: 

 * N-dimension array: 
For multivariate signal analysis, n-dim array are very important. (e.g. 
multivariate autoregressive parameters are a sequence of matrices; and 
repeations of multichannel recordings). I'm able to handle this type of data 
with the current octave (i.e. two-dimensional matrices) using some workarounds 
(e.g. see TSA/MVAR). For this reason, N-dimensional arrays are not an important 
topic. It is not crucial, if the implementation of N-dim is delayed. In the 
list, N-dim arrays can be moved further down to a less important position. 


 * Sparse matrices: 
An important issue is the matrix multiplication of full and sparse matrices. 
See the following example:

x = [-inf, -1, 0, 1, inf,nan];
sx= sparse(x);
full(x'*x)
full(sx'*sx)

The point is that under some circumstances (0*inf, 0*-inf, 0*nan), matrix 
multiplications of full and sparse matrices give different results. 
SPARSE can be used to control the desired behavior. Therefore, SPARSE is 
important and, currently, there is no workaround. IMHO, SPARSE has top 
priority. 

These are my few thougths, 
   Alois 



> My current top 10 list is, more or less in order of importance:
> 
>   * some support for MPI
> 
>   * N-dimensional arrays
> 
>   * sparse matrices
> 
>   * clean up the load-save mess
> 
>   * extend cell arrays, struct arrays, and function handles to also be
>     N-dimensional
> 
>   * finish implementation of cell arrays and struct arrays:
>       -- cell(idx) = [] to delete elements
>       -- a(1).x = 1; a(2).x = 2; a.x => c.s. list, [a.x] => num array
>       -- allow [x{:}] = f (...) to work
>       -- and other little details like this...
> 
>   * [ ... ] should concatenate array-like objects other than matrices
> 
>   * inline functions
> 
>   * private functions
> 
>   * bring the manual up to date

-- 



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