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.TH spantwo 1 "April 1993" "Scilab Group" "Scilab Function"
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spantwo - sum and intersection of subspaces
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[Xp,dima,dimb,dim]=spantwo(A,B, [tol])
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: two real or complex matrices with equal number of rows
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: square non-singular matrix
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: integers, dimension of subspaces
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: nonnegative real number
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Given two matrices \fVA\fR and \fVB\fR with same number of rows,
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returns a square matrix \fVXp\fR (non singular but not necessarily orthogonal)
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[A1, 0] (dim-dimb rows)
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Xp*[A,B]=[A2,B2] (dima+dimb-dim rows)
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[0, B3] (dim-dima rows)
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The first \fVdima\fR columns of \fVinv(Xp)\fR span range(\fVA\fR).
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Columns \fVdim-dimb+1\fR to \fVdima\fR of \fVinv(Xp)\fR span the
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intersection of range(A) and range(B).
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The \fVdim\fR first columns of \fVinv(Xp)\fR span
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range(\fVA\fR)+range(\fVB\fR).
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Columns \fVdim-dimb+1\fR to \fVdim\fR of \fVinv(Xp)\fR span
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Matrix \fV[A1;A2]\fR has full row rank (=rank(A)). Matrix \fV[B2;B3]\fR has
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full row rank (=rank(B)). Matrix \fV[A2,B2]\fR has full row rank (=rank(A inter B)). Matrix \fV[A1,0;A2,B2;0,B3]\fR has full row rank (=rank(A+B)).
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B=[1,2,0,0]';C=[4,0,0,1];
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Sl=ss2ss(syslin('c',A,B,C),rand(A));
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[no,X]=contr(Sl('A'),Sl('B'));CO=X(:,1:no); //Controllable part
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[uo,Y]=unobs(Sl('A'),Sl('C'));UO=Y(:,1:uo); //Unobservable part
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[Xp,dimc,dimu,dim]=spantwo(CO,UO); //Kalman decomposition
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Slcan=ss2ss(Sl,inv(Xp));