function b = r85_to_r8ge ( n, a ) %*****************************************************************************80 % %% R85_TO_R8GE copies a R85 matrix into a R8GE matrix. % % Discussion: % % The R85 storage format represents a pentadiagonal matrix as a 5 % by N array, in which each row corresponds to a diagonal, and % column locations are preserved. Thus, the original matrix is % "collapsed" vertically into the array. % % Example: % % Here is how a R85 matrix of order 6 would be stored: % % * * A13 A24 A35 A46 % * A12 A23 A34 A45 A56 % A11 A22 A33 A44 A55 A66 % A21 A32 A43 A54 A65 * % A31 A42 A53 A64 * * % % Licensing: % % This code is distributed under the GNU LGPL license. % % Modified: % % 03 February 2004 % % Author: % % John Burkardt % % Parameters: % % Input, integer N, the order of the matrix. % N must be at least 3. % % Input, real A(5,N), the R85 matrix. % % Output, real A(N,N), the R8GE matrix. % for i = 1 : n for j = 1 : n if ( j == i-2 ) b(i,j) = a(1,i); elseif ( j == i-1 ) b(i,j) = a(2,i); elseif ( i == j ) b(i,j) = a(3,i); elseif ( j == i+1 ) b(i,j) = a(4,i); elseif ( j == i+2 ) b(i,j) = a(5,i); else b(i,j) = 0.0; end end end return end