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<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
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<!DOCTYPE MAN SYSTEM "../../manrev.dtd">
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<LANGUAGE>fr</LANGUAGE>
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<TYPE>Scilab Function </TYPE>
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<DATE>April 1993 </DATE>
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<SHORT_DESCRIPTION name="pbig"> projection sur des sous-espaces propres </SHORT_DESCRIPTION>
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<CALLING_SEQUENCE_ITEM>[Q,M]=pbig(A,thres,flag) </CALLING_SEQUENCE_ITEM>
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<PARAM_NAME>A </PARAM_NAME>
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: matrice r�elle carr�e
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<PARAM_NAME>thres </PARAM_NAME>
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<PARAM_NAME>flag </PARAM_NAME>
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: cha�ne de caract�res (<VERB>'c'</VERB> ou <VERB>'d'</VERB>)
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<PARAM_NAME>Q,M </PARAM_NAME>
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Projection sur des sous-espaces propres de A associ�s aux valeurs
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propres avec partie r�elle >= <VERB>thres</VERB>
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(<VERB>flag='c'</VERB>) ou avec module >=
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<VERB>thres</VERB> (<VERB>flag='d'</VERB>).
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La projection est d�finie par <VERB>Q*M</VERB>, o� <VERB>Q</VERB>
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est de rang maximal, les lignes de <VERB>M</VERB> sont
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lin�airement ind�pendantes et <VERB>M*Q=eye</VERB>.
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Si <VERB>flag='c'</VERB>, les valeurs propres de
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<VERB>M*A*Q</VERB> = valeurs propres de <VERB>A</VERB> avec partie
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r�elle >= <VERB>thres</VERB>.
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Si <VERB>flag='d'</VERB>, les valeurs propres de
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<VERB>M*A*Q</VERB> = valeurs propres de <VERB>A</VERB> avec module
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>= <VERB>thres</VERB>.
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Si <VERB>flag='c'</VERB> et si <VERB>[Q1,M1]</VERB> =
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factorisation de rang maximal (<VERB>fullrf</VERB>) de
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<VERB>eye()-Q*M</VERB> alors les valeurs propres de
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<VERB>M1*A*Q1</VERB> = valeurs propres de <VERB>A</VERB> avec
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partie r�elle < <VERB>thres</VERB>.
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Si <VERB>flag='d'</VERB> et si <VERB>[Q1,M1]</VERB> =
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factorisation de rang maximal (<VERB>fullrf</VERB>) de
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<VERB>eye()-Q*M</VERB> alors les valeurs propres de
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<VERB>M1*A*Q1</VERB> = valeurs propres de <VERB>A</VERB> avec
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module < <VERB>thres</VERB>.
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A=diag([1,2,3]);X=rand(A);A=inv(X)*A*X;
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[Q,M]=pbig(A,1.5,'d');
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[Q1,M1]=fullrf(eye()-Q*M);
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<SEE_ALSO_ITEM> <LINK>psmall</LINK> </SEE_ALSO_ITEM>
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<SEE_ALSO_ITEM> <LINK>projspec</LINK> </SEE_ALSO_ITEM>
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<SEE_ALSO_ITEM> <LINK>fullrf</LINK> </SEE_ALSO_ITEM>
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<SEE_ALSO_ITEM> <LINK>schur</LINK> </SEE_ALSO_ITEM>
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<AUTHOR>F. Delebecque, INRIA (1988); ; </AUTHOR>
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<SP><VERB>pbig</VERB> est bas�e sur la forme de Schur ordonn�e
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(fonction Scilab <VERB>schur</VERB>).</SP>