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Ren et al. (2018)<ref name="ren18" /> are able to prove the stability of NMF components when they are constructed sequentially (i.e., one by one), which enables the [[linearity]] of the NMF modeling process; the [[linearity]] property is used to separate the stellar light and the light scattered from the [[exoplanets]] and [[circumstellar disks]].
In direct imaging, to reveal the faint exoplanets and circumstellar disks from bright the surrounding stellar lights, which has a typical contrast from 10⁵ to 10¹⁰, various statistical methods have been adopted,<ref>{{Cite journal |arxiv=0902.3247 |last1=Lafrenière|first1=David |title=HST/NICMOS Detection of HR 8799 b in 1998 |journal=The Astrophysical Journal Letters |volume=694|issue=2|pages=L148|last2=Maroid |first2= Christian|last3= Doyon |first3=René| last4=Barman|first4=Travis|date=2009|doi=10.1088/0004-637X/694/2/L148|bibcode=2009ApJ...694L.148L |s2cid=7332750}}</ref><ref>{{Cite journal|arxiv=1207.6637 |last1= Amara|first1= Adam |title= PYNPOINT: an image processing package for finding exoplanets|journal= Monthly Notices of the Royal Astronomical Society|volume= 427|issue= 2|pages= 948|last2= Quanz|first2= Sascha P.|date= 2012|doi= 10.1111/j.1365-2966.2012.21918.x|doi-access= free|bibcode = 2012MNRAS.427..948A|s2cid= 119200505}}</ref><ref name = "soummer12">{{Cite journal|arxiv=1207.4197|last1= Soummer|first1= Rémi |title= Detection and Characterization of Exoplanets and Disks Using Projections on Karhunen-Loève Eigenimages|journal= The Astrophysical Journal Letters |volume= 755|issue= 2|pages= L28|last2= Pueyo|first2= Laurent|last3= Larkin |first3=James|date=2012|doi=10.1088/2041-8205/755/2/L28|bibcode=2012ApJ...755L..28S|s2cid=51088743}}</ref> however the light from the exoplanets or circumstellar disks are usually over-fitted, where forward modeling have to be adopted to recover the true flux.<ref>{{Cite journal|arxiv= 1502.03092 |last1= Wahhaj |first1= Zahed |title=Improving signal-to-noise in the direct imaging of exoplanets and circumstellar disks with MLOCI |last2=Cieza|first2=Lucas A.|last3=Mawet|first3=Dimitri|last4=Yang|first4=Bin|last5=Canovas |first5=Hector|last6=de Boer|first6=Jozua|last7=Casassus |first7=Simon|last8= Ménard|first8= François |last9=Schreiber|first9=Matthias R.|last10=Liu|first10=Michael C.|last11=Biller|first11=Beth A. |last12=Nielsen|first12=Eric L.|last13=Hayward|first13=Thomas L.|journal= Astronomy & Astrophysics|volume= 581|issue= 24|pages= A24|date=2015|doi= 10.1051/0004-6361/201525837|bibcode = 2015A&A...581A..24W|s2cid= 20174209}}</ref><ref name="pueyo16">{{Cite journal|arxiv= 1604.06097 |last1= Pueyo|first1= Laurent |title= Detection and Characterization of Exoplanets using Projections on Karhunen Loeve Eigenimages: Forward Modeling |journal= The Astrophysical Journal |volume= 824|issue= 2|pages= 117|date= 2016|doi= 10.3847/0004-637X/824/2/117 |bibcode = 2016ApJ...824..117P|s2cid= 118349503|doi-access= free}}</ref> Forward modeling is currently optimized for point sources,<ref name="pueyo16"/> however not for extended sources, especially for irregularly shaped structures such as circumstellar disks. In this situation, NMF has been an excellent method, being less over-fitting in the sense of the non-negativity and [[sparsity]] of the NMF modeling coefficients, therefore forward modeling can be performed with a few scaling factors,<ref name="ren18" /> rather than a computationally intensive data re-reduction on generated models.
=== Data imputation ===
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