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Usage:
triupper(A [,pack:T]), A a matrix
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Keywords:
matrix algebra, variables, combining variables
triupper(a) returns a matrix d of the same size and shape as a with
d[i,j] = a[i,j] for i <= j (on or above the diagonal) and d[i,j] = 0 for
i > j (below diagonal). Variable a must be a matrix but need not be
square.
[1 5 9] [1 5 9]
For example, when a is [2 6 10] , triupper(a) is [0 6 10]
[3 7 11] [0 0 11]
[4 8 12] [0 0 0]
triupper(a,square:T) returns the m by m upper left block of triupper(a),
where m = min(nrows(a),ncols(a)).
When a has type CHARACTER, elements below the diagonal are sent to empty
strings ("") instead of 0's.
triupper(a,T) or triupper(a,pack:T) returns the upper triangle (elements
a[i,j] with i <= j) of a in packed form. Matrix a must be square, that
is, nrows(a) = ncols(a). For example, when
[1 4 7]
a = [2 5 8]
[3 6 9]
triupper(a,pack:T) is vector(1, 4, 5, 7, 8, 9).
See also trilower(), triunpack(), qr().
Gary Oehlert
2003-01-15