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Create or extract symbolic diagonals.
diag(A,k) diag(A)
diag(A,k), where A is a row or column vector with n components, returns a square symbolic matrix of order n+abs(k), with the elements of A on the k-th diagonal. k = 0 signifies the main diagonal; k > 0, the k-th diagonal above the main diagonal; k < 0, the k-th diagonal below the main diagonal.
diag(A,k), where A is a square symbolic matrix, returns a column vector formed from the elements of the k-th diagonal of A.
diag(A), where A is a vector with n components, returns an n-by-n diagonal matrix having A as its main diagonal.
diag(A), where A is a square symbolic matrix, returns the main diagonal of A.
Suppose
v = [a b c]Then both
diag(v) and diag(v,0) return
[ a, 0, 0 ] [ 0, b, 0 ] [ 0, 0, c ]
diag(v,-2) returns
[ 0, 0, 0, 0, 0] [ 0, 0, 0, 0, 0] [ a, 0, 0, 0, 0] [ 0, b, 0, 0, 0] [ 0, 0, c, 0, 0]Suppose
A = [ a, b, c ] [ 1, 2, 3 ] [ x, y, z ]
diag(A) returns
[ a ] [ 2 ] [ z ]
diag(A,1) returns
[ b ] [ 3 ]
tril, triu