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spaninter(1) Scilab Function spaninter(1)
NAME
spaninter - subspace intersection
CALLING SEQUENCE
[X,dim]=spaninter(A,B [,tol])
PARAMETERS
A, B : two real or complex matrices with equal number of rows
X : orthogonal or unitary square matrix
dim : integer, dimension of subspace range(A) inter range(B)
DESCRIPTION
[X,dim]=spaninter(A,B) computes the intersection of range(A) and range(B).
The first dim columns of X span this intersection i.e. X(:,1:dim) is an
orthogonal basis for
range(A) inter range(B)
In the X basis A and B are respectively represented by:
X'*A and X'*B.
tol is a threshold (sqrt(%eps) is the default value).
EXAMPLE
A=rand(5,3)*rand(3,4); // A is 5 x 4, rank=3
B=[A(:,2),rand(5,1)]*rand(2,2);
[X,dim]=spaninter(A,B);
X1=X(:,1:dim); //The intersection
svd(A),svd([X1,A]) // X1 in span(A)
svd(B),svd([B,X1]) // X1 in span(B)
SEE ALSO
spanplus, spantwo
AUTHOR
F. D.
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