function table = p_exponential_product ( p, b ) %*****************************************************************************80 % %% P_EXPONENTIAL_PRODUCT: exponential products for P(n,x). % % Discussion: % % Let P(n,x) represent the Legendre polynomial of degree i. % % For polynomial chaos applications, it is of interest to know the % value of the integrals of products of exp(B*X) with every possible pair % of basis functions. That is, we'd like to form % % Tij = Integral ( -1 <= X <= +1 ) exp(B*x) * P(i,x) * P(j,x) dx % % Because of the exponential factor, the quadrature will not be exact. % % Licensing: % % This code is distributed under the GNU LGPL license. % % Modified: % % 13 March 2012 % % Author: % % John Burkardt % % Parameters: % % Input, integer P, the maximum degree of the polyonomial factors. % 0 <= P. % % Input, real B, the coefficient of X in the exponential factor. % % Output, real TABLE(P+1,P+1), the table of integrals. % table(1:p+1,1:p+1) = 0.0; order = floor ( ( 3 * p + 4 ) / 2 ); [ x_table, w_table ] = p_quadrature_rule ( order ); for k = 1 : order x = x_table(k); l_table = p_polynomial ( 1, p, x ); % % The following formula is an outer product in L_TABLE. % table(1:p+1,1:p+1) = table(1:p+1,1:p+1) ... + w_table(k) * exp ( b * x ) * l_table(1:p+1)' * l_table(1:p+1); end return end