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  2. Kirchhoff's theorem - Wikipedia

    en.wikipedia.org/wiki/Kirchhoff's_theorem

    (The proof below is based on the Cauchy–Binet formula.An elementary induction argument for Kirchhoff's theorem can be found on page 654 of Moore (2011). [2]) First notice that the Laplacian matrix has the property that the sum of its entries across any row and any column is 0.

  3. Matrix addition - Wikipedia

    en.wikipedia.org/wiki/Matrix_addition

    Two matrices must have an equal number of rows and columns to be added. [1] In which case, the sum of two matrices A and B will be a matrix which has the same number of rows and columns as A and B. The sum of A and B, denoted A + B, is computed by adding corresponding elements of A and B: [2] [3]

  4. Monge array - Wikipedia

    en.wikipedia.org/wiki/Monge_array

    So for any two rows and two columns of a Monge array (a 2 × 2 sub-matrix) the four elements at the intersection points have the property that the sum of the upper-left and lower right elements (across the main diagonal) is less than or equal to the sum of the lower-left and upper-right elements (across the antidiagonal).

  5. Matrix multiplication - Wikipedia

    en.wikipedia.org/wiki/Matrix_multiplication

    Given three matrices A, B and C, the products (AB)C and A(BC) are defined if and only if the number of columns of A equals the number of rows of B, and the number of columns of B equals the number of rows of C (in particular, if one of the products is defined, then the

  6. Stochastic matrix - Wikipedia

    en.wikipedia.org/wiki/Stochastic_matrix

    The above elementwise sum across each row i of P may be more concisely written as P1 = 1, where 1 is the α-dimensional column vector of all ones. Using this, it can be seen that the product of two right stochastic matrices P′ and P′′ is also right stochastic: P′ P′′ 1 = P′ (P′′ 1) = P′ 1 = 1.

  7. List of named matrices - Wikipedia

    en.wikipedia.org/wiki/List_of_named_matrices

    A row consists of 1, a, a 2, a 3, etc., and each row uses a different variable. Walsh matrix: A square matrix, with dimensions a power of 2, the entries of which are +1 or −1, and the property that the dot product of any two distinct rows (or columns) is zero. Z-matrix: A matrix with all off-diagonal entries less than zero.

  8. Matrix (mathematics) - Wikipedia

    en.wikipedia.org/wiki/Matrix_(mathematics)

    A matrix with the same number of rows and columns is called a square matrix. [5] A matrix with an infinite number of rows or columns (or both) is called an infinite matrix. In some contexts, such as computer algebra programs, it is useful to consider a matrix with no rows or no columns, called an empty matrix.

  9. Magic square - Wikipedia

    en.wikipedia.org/wiki/Magic_square

    During the construction of the 3×3 magic square, the Greek and Latin squares with just three unique terms are much easier to deal with than the original square with nine different terms. The row sum and the column sum of the Greek square will be the same, α + β + γ, if each letter appears exactly once in a given column or a row.