Vectorize a code that finds the roots of polynomials stored in matrices
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I need some tips on how to vectorize a code that finds the roots of polynomials stored in matrices. What I have is a multidimensional array that contains 100 matrices of 100-by-3 size. I'm pasting the code below
one = ones ( 100, 100 );
poly.struc = reshape( [ one; gr_fac1; - gr_fac2 ], 100, 3, [] );
poly_roots_select = zeros ( 100, 100);
for j = 1:1:100
poly_matrices = poly.struc ( :, :, j );
for i = 1:1:100
poly_select = poly_matrices ( i, : );
poly_roots = roots ( poly_select );
poly_roots_select ( i , j) = poly_roots ( real ( poly_roots) > 0 , 1 ) ;
end
end
I would like to remove both for loops. At minimum I like to be able to access the matrices stored in poly.struc array without putting a loop for this. Is there also any other way to be able to pass a row vectors from a matrix to roots function without needing a loop?
Thanks in advance
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Thorsten
le 7 Fév 2013
The roots function only accepts vectors.
You may speed up your code by getting rid of the two intermediate variables poly_matrices and poly_select:
for j = 1:1:100
for i = 1:1:100
poly_roots = roots ( poly.struc ( i, :, j ) );
poly_roots_select ( i , j ) = poly_roots ( real ( poly_roots) > 0 , 1 ) ;
end
end
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