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spdiags

PURPOSE ^

% A generalization of the function @code{diag}. Called with a single

SYNOPSIS ^

function [A, c] = spdiags (v, c, m, n)

DESCRIPTION ^

% -*- texinfo -*-
% @deftypefn {Function File} {[@var{b}, @var{c}] =} spdiags (@var{a})
% @deftypefnx {Function File} {@var{b} =} spdiags (@var{a}, @var{c})
% @deftypefnx {Function File} {@var{b} =} spdiags (@var{v}, @var{c}, @var{a})
% @deftypefnx {Function File} {@var{b} =} spdiags (@var{v}, @var{c}, @var{m}, @var{n})
% A generalization of the function @code{diag}.  Called with a single
% input argument, the non-zero diagonals @var{c} of @var{A} are extracted.
% With two arguments the diagonals to extract are given by the vector 
% @var{c}.
%
% The other two forms of @code{spdiags} modify the input matrix by
% replacing the diagonals.  They use the columns of @var{v} to replace
% the columns represented by the vector @var{c}.  If the sparse matrix
% @var{a} is defined then the diagonals of this matrix are replaced.
% Otherwise a matrix of @var{m} by @var{n} is created with the
% diagonals given by @var{v}.
%
% Negative values of @var{c} represent diagonals below the main
% diagonal, and positive values of @var{c} diagonals above the main
% diagonal.
%
% For example
%
% @example
% @group
% spdiags (reshape (1:12, 4, 3), [-1 0 1], 5, 4)
% @result{}    5 10  0  0
%       1  6 11  0
%       0  2  7 12
%       0  0  3  8
%       0  0  0  4
% @end group
% @end example
%
% @end deftypefn

CROSS-REFERENCE INFORMATION ^

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