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Documentation confusing around eigenvector naming #54

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philippdahm opened this issue Feb 12, 2023 · 1 comment
Open

Documentation confusing around eigenvector naming #54

philippdahm opened this issue Feb 12, 2023 · 1 comment

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@philippdahm
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philippdahm commented Feb 12, 2023

Hey,
I might be completely off base here, but the documentation seems to reference the eigenvectors as both "U" (L149) and then later on line 139 as "V" i was wondering if this is a mistake on my understanding or a simple typo.

modred/modred/pod.py

Lines 137 to 140 in bbe35c8

* ``eigvecs``: Array wholse columns are eigenvectors of correlation
array (:math:`U`).

modred/modred/pod.py

Lines 148 to 152 in bbe35c8

where :math:`X`, :math:`W`, :math:`S`, :math:`V`, correspond to
``vecs``, ``inner_product_weights``, ``eigvals**0.5``,
and ``eigvecs``, respectively.

please let me know what comes of this and thanks so much for creating this. has certainly helped me substantially!
best,
Phil

@jhtu
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jhtu commented Feb 13, 2023

Hi Phil,

Glad to hear you are using modred.  I think this is a typo, but I want to double check for sure, and will need a bit of time.  You can check the dimensions though, for an empirical check.  If you have X as an $n \times m$ array, then U should be $n \times r$, where $r$ is the number of modes/singular values, and V should be $m \times r$.  This is for the situation $X = U \Sigma V^*$.  

Jonathan Tu

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