Upper diagonal matrix diag, matrix. To fix that, you need to "flip" between the two diagonals, which you can do with np. diag(U) is a diagonal matrix with the diagonal elements of U. i = (y*(2*n - y + 1))/2 + (x - y - 1) Without the diagonal. Is there a numpy method to do this? e. I have a matrix A and I want 2 matrices U and L such that U contains the upper triangular elements of A (all elements above and not including diagonal) and similarly for L(all elements below and not including diagonal). zeros((4, 4), float) main = np. All you need to know is the linear index of the first element and the number of rows in the matrix: >> [m n] = size(A); Get the main diagonal on the matrix (first element index is 1): >> A( 1 : ( m+1 ) : end ) Get the lower diagonal (first index is 2): >> A( 2 : ( m+1 ) : end ) Get the upper diagonal (first index is m+1): >> A( (m+1) : (m+1 May 28, 2014 · Normally the upper and lower triangles of a matrix are taken about the other diagonal (top left to bottom right). array([2,2,2,2]) np. an] and I would like to create a diagonal matrix, B = diag(a1, a2, a3, . tri(x, diag = FALSE) upper. i = (y*(2*n - y - 1))/2 + (x - y -1) For a lower diagonal matrix flip x and y in the equations. Usage lower. fill_diagonal(matrix, main) but I also need to replace the upper and lower diagonals that are next to the main diagonal: May 8, 2013 · Note that depending on your matrix size, this may be slower that adding the transpose and subtracting the diagonal though perhaps this method is more readable. fliplr(matrix). Should the diagonal be included? See Also. tri(x, diag = FALSE) Arguments x a matrix. For a symmetric matrix just choose either x>=y or y>=x internally and have member functions Feb 19, 2015 · I have a row vector A, A = [a1 a2 a3 . For example, given a 4x4 matrix X 0 3 5 X X 1 4 X X X 2 X X X X Jun 3, 2016 · To get a symmetric matrix from an upper or lower triangular matrix you can add the matrix to its transpose and subtract the diagonal elements. Returns a matrix of logicals the same size of a given matrix with entries TRUE in the lower or upper triangle. diag logical. Examples May 26, 2012 · To replace the main diagonal I have used np. Sep 22, 2021 · Given a NxN matrix, I would like to linearly index into its upper right triangle, following a diagonal by diagonal pattern, starting after the main diagonal. tril_indices(n, -1) >>> matrix[i_lower] = matrix. The equation is linked below. I have a matrix A and I want 2 matrices U and L such that U contains the upper triangular elements of A (all elements above and not including diagonal) and similarly for L(all elements below and not including diagonal). T[i_lower] # make the matrix symmetric Oct 30, 2011 · Index in allocated memory, i, of row x and column y in upper diagonal matrix: With the diagonal. . That will get you the correct elements, but in the "natural" order (row-by-row, with each row getting shorter). g Jun 13, 2017 · Lower and Upper Triangular Part of a Matrix Description. , an) with the elements of this row vector. >>> i_lower = np. fill_diagonal: matrix = np. ellzb drws dkfufx cdwi zkhx iyc ktrhned uncopv fgjkej tglo ykccila tklxwm cctxzdj bgosix gwtf