function [H,dH]=gmmh(theta);
%GMMH   A user-supplied function for GMM estimation.
%       [H,dH]=gmmh(theta) is called by GMM and GMMJ. H is a
%       nobs x m (or mgmm) matrix with rows containing the m x 1 
%       vectors h(x(t+n),theta), where it is assumed that
%
%           E[ h(x(t+n),theta) | I(t) ] = 0,  t=1,...,nobs.
%
%       dH is a nobs x (m*l) matrix containing the derivatives
%       of H with respect to the elements of theta, i.e.
%       dH(t,:)= [dh1(x(t+n),theta)/dtheta', ... 
%                                 dhm(x(t+n),theta)/dtheta']
%

%       Code for H, dH from example in:
%         Hansen, L.P. and K.J. Singleton, "Generalized Instrumental
%         Variables Estimation of Nonlinear Rational Expectations
%         Models," ECONOMETRICA, 50:1269-1286, 1982, pp. 1281-1282.

%

beta  = theta(1);
alpha = theta(2);

H=beta*xgmm(:,1).^alpha.*xgmm(:,2)-1;

if nargout>1;
  dH=[(H+1)/beta,(H+1).*log(xgmm(:,1))];
end;