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<!DOCTYPE article PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Publishing DTD v1.0 20120330//EN" "JATS-journalpublishing1.dtd"><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" article-type="research-article"><front><journal-meta><journal-id journal-id-type="publisher-id">INFORMATICA</journal-id><journal-title-group><journal-title>Informatica</journal-title></journal-title-group><issn pub-type="epub">0868-4952</issn><issn pub-type="ppub">0868-4952</issn><publisher><publisher-name>VU</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="publisher-id">inf22402</article-id><article-id pub-id-type="doi">10.15388/Informatica.2011.338</article-id><article-categories><subj-group subj-group-type="heading"><subject>Research article</subject></subj-group></article-categories><title-group><article-title>Analysis of Structured Low Rank Approximation as an Optimization Problem</article-title></title-group><contrib-group><contrib contrib-type="Author"><name><surname>Gillard</surname><given-names>Jonathan</given-names></name><email xlink:href="mailto:gillardjw@cardiff.ac.uk">gillardjw@cardiff.ac.uk</email></contrib><contrib contrib-type="Author"><name><surname>Zhigljavsky</surname><given-names>Anatoly</given-names></name><email xlink:href="mailto:zhigljavskyaa@cardiff.ac.uk">zhigljavskyaa@cardiff.ac.uk</email></contrib><aff>Cardiff School of Mathematics, Cardiff University, Senghenydd Road, Cardiff, UK</aff></contrib-group><pub-date pub-type="epub"><day>01</day><month>01</month><year>2011</year></pub-date><volume>22</volume><issue>4</issue><fpage>489</fpage><lpage>505</lpage><history><date date-type="received"><day>01</day><month>06</month><year>2011</year></date><date date-type="accepted"><day>01</day><month>09</month><year>2011</year></date></history><abstract><p>In this paper, we consider the so-called structured low rank approximation (SLRA) problem as a problem of optimization on the set of either matrices or vectors. Briefly, SLRA is defined as follows. Given an initial matrix with a certain structure (for example, Hankel), the aim is to find a matrix of specified lower rank that approximates this initial matrix, whilst maintaining the initial structure. We demonstrate that the optimization problem arising is typically very difficult; in particular, the objective function is multiextremal even in simple cases. We also look at different methods of solving the SLRA problem. We show that some traditional methods do not even converge to a locally optimal matrix.</p></abstract><kwd-group><label>Keywords</label><kwd>structured low rank approximation</kwd><kwd>Hankel matrix</kwd><kwd>optimization</kwd></kwd-group></article-meta></front></article>