function output = struveh1approx2(x)
% Struve H1 routine that evaluates the asymptotic expansion for large arguments and
% the series expansion for small arguments
%
% Robert J. McGough
% Michigan State University
% 18 Dec 2005

ixle4 = find(x <= 4.7);
x2 = x.^2;
output(ixle4) = 2/pi * (x2(ixle4) / 3 - x2(ixle4).^2 / 3^2 / 5 + x2(ixle4).^3 / 3^2 / 5^2 / 7 - x2(ixle4).^4 / 3^2 / 5^2 / 7^2 / 9 + x2(ixle4).^5 / 3^2 / 5^2 / 7^2 / 9^2 / 11 - + x2(ixle4).^6 / 3^2 / 5^2 / 7^2 / 9^2 / 11^2 / 13);
ixgt4 = find(x > 4.7);
output(ixgt4) = 2/pi - sqrt(2 / pi ./ x(ixgt4)) .* cos(x(ixgt4) - pi / 4);