I've got a method for visualising non-zero $2 \times 2$ real matrices (modulo non-zero scalar factor) using the fact that:
- Nonnegative determinant matrices (modulo non-zero scalar factor) are in 1-to-1 correspondence with hyperbolic cycles in the hyperbolic plane, endowed with orientation
- Nonpositive determinant matrices (modulo non-zero scalar factor) are in 1-to-1 correspondence with "pencils of lines of equal inclination" in the hyperbolic plane
The significance is that this depicts:
- The eigenvalues of a matrix
- Its eigenvectors
- Its condition number
- Its Jordan normal form
- What it's orthogonally similar to
- Whether it is diagonal
- Or upper triangular
- Or lower triangular
- Or symmetric
- Or orthogonal
The question arises: Are there other methods for visualising general matrices, which convey properties which are significant for linear algebra? I'm especially interested in techniques valid for $3 \times 3$ matrices.
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