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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>eng</LANGUAGE>
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<TITLE>spanplus</TITLE>
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<TYPE>Scilab Function</TYPE>
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<DATE>April 1993</DATE>
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<SHORT_DESCRIPTION name="spanplus"> sum of subspaces</SHORT_DESCRIPTION>
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<CALLING_SEQUENCE_ITEM>[X,dim,dima]=spanplus(A,B[,tol]) </CALLING_SEQUENCE_ITEM>
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<PARAM_NAME>A, B</PARAM_NAME>
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<SP>: two real or complex matrices with equal number of rows</SP>
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<PARAM_NAME>X</PARAM_NAME>
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<SP>: orthogonal or unitary square matrix</SP>
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<PARAM_NAME>dim, dima</PARAM_NAME>
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<SP>: integers, dimension of subspaces</SP>
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<PARAM_NAME>tol</PARAM_NAME>
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<SP>: nonnegative real number</SP>
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computes a basis X such that:</P>
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the first <VERB>dima</VERB> columns of <VERB>X</VERB> span Range(<VERB>A</VERB>)
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and the following (<VERB>dim-dima</VERB>) columns make a basis of <VERB>A+B</VERB>
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relative to <VERB>A</VERB>.</P>
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The <VERB>dim</VERB> first columns of <VERB>X</VERB> make a basis for <VERB>A+B</VERB>.</P>
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One has the following canonical form for <VERB>[A,B]</VERB>:</P>
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X'*[A,B]=[0,*] (dim-dima rows)
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<P><VERB>tol</VERB> is an optional argument (see function code).</P>
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A=rand(6,2)*rand(2,5); // rank(A)=2
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B=[A(:,1),rand(6,2)]*rand(3,3); //two additional independent vectors
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[X,dim,dimA]=spanplus(A,B);
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<LINK>spaninter</LINK>
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<AUTHOR>F. D.; ; </AUTHOR>