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create a diagonal matrix

  1. osigrtoeltParticipant 2010-12-16 at 10:00 am

    What is the best way to create an identity matrix in SuanShu? How about other diagonal matrices? Thanks.

  2. Haksun LiModerator 2010-12-16 at 10:08 am

    From any [tt:v42epeki]DenseMatrix[/tt:v42epeki] A, you can create the identity matrix by calling

    <br />
Matrix I = A.ONE();<br />

    If you don’t already have a matrix but know the dimension, you can do

    <br />
Matrix I = new DenseMatrix(2, 2).ONE();<br />

    To create a diagonal matrix from another matrix A, you can do

    <br />
Matrix D = CreateMatrix.diagonalMatrix(A);<br />

  3. osigrtoeltParticipant 2010-12-16 at 10:13 am

    What should I do if I would to create a 5 by 5 diagonal matrix with entries {1, 2, 3, 4, 5} on the main diagonal?

  4. Haksun LiModerator 2010-12-16 at 1:53 pm 

    <br />
DiagonalMatrix instance = new DiagonalMatrix(new double[]{1, 2, 3, 4, 5});<br />

  5. osigrtoeltParticipant 2010-12-17 at 2:35 am

    How do we coerce a Matrix to a DenseMatrix?

    For instance,

    Matrix I = new DenseMatrix(2, 2).ONE();

    I becomes a Matrix and I.setColumn() doesn’t seem to work.

    Any help would be greatly appreciated.

  6. Haksun LiModerator 2010-12-17 at 5:49 am

    Maybe declare I as a [tt:3g6j7frh]DenseMatrix[/tt:3g6j7frh] to start with?

    <br />
DenseMatrix I = new DenseMatrix(2, 2).ONE();<br />

  7. osigrtoeltParticipant 2010-12-17 at 7:31 am

    No, that yields ‘incompatible types’, since DenseMatrix(int, int).ONE() is of type Matrix. Please correct me if I’m wrong.

    I’m currently doing something like this, but it seems cumbersome:

    DenseMatrix I = new DenseMatrix(new DenseMatrix(2, 2).ONE());