assemble the ei values at each node into a diagonal matrix: in matlab

To assemble the eigenvalues (ei) at each node into a diagonal matrix in MATLAB, you can use the following code:

main.m
% Example data
ei = [1 2 3 4];

% Assemble diagonal matrix
diagonal_matrix = diag(ei);
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In this example, ei is an array containing the eigenvalues at each node. The diag function in MATLAB creates a diagonal matrix with the input values placed on the main diagonal.

The resulting diagonal_matrix will be:

main.m
1  0  0  0
0  2  0  0
0  0  3  0
0  0  0  4
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Each eigenvalue is placed on the diagonal of the matrix, and all other elements are set to zero.