Triangular Matrices (Matlab Style)
Extract lower or upper triangular part of a matrix.
tril(M, k = 0) triu(M, k = 0)
M |
numeric matrix. |
k |
integer, indicating a secondary diagonal. |
tril
Returns the elements on and below the kth diagonal of X, where k = 0 is
the main diagonal, k > 0 is above the main diagonal, and k < 0 is below
the main diagonal.
triu
Returns the elements on and above the kth diagonal of X, where k = 0 is
the main diagonal, k > 0 is above the main diagonal, and k < 0 is below
the main diagonal.
Matrix the same size as the input matrix.
For k==0 it is simply an application of the R functions
lower.tri resp. upper.tri.
tril(ones(4,4), +1) # 1 1 0 0 # 1 1 1 0 # 1 1 1 1 # 1 1 1 1 triu(ones(4,4), -1) # 1 1 1 1 # 1 1 1 1 # 0 1 1 1 # 0 0 1 1
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