在网上下的源码,缺少fxa函数,谁知道fxa去哪里下载?

function [p,u,E]=trainGMM(x,pin,ui,Ei,n,M)

% function [p,u,E]=trainGMM(x,pin,ui,Ei,n,M)
%
% Train GMM of order M with the EM algorithm, using training data y and
% initial conditions ini.
%
% x - training data
% pin - initial p
% ui - initial u
% Ei - initial E
% M - number of mixtures
% n - iterations
%
% p - model weights
% u - model means
% E - model variance matrices

[T,D]=size(x);

p=pin;
u=ui;
for i=1:M

  E(:,:,i)=Ei(:,:,i);
  o(i,:)=diag(Ei(:,:,i))';
end

for j=1:n
  for t=1:T
    c(t)=0;
    for k=1:M
      c(t)=c(t)+p(k)*fxa(u(k,:),E(:,:,k),inv(E(:,:,k)),x(t,:));
      %1/((2*pi)^(D/2)*sqrt(det(E)));
    end
  end

  for i=1:M
    [j,i];
    a1=0;
    a2=zeros(1,D);
    a3=zeros(1,D);

    invE=inv(E(:,:,i));
    for t=1:T
      ap=p(i)*fxa(u(i,:),E(:,:,i),invE,x(t,:))/c(t);
      a1=a1+ap;
      a2=a2+ap*x(t,:);
      a3=a3+ap*x(t,:).^2;
    end

    % update parameters
    p(i)=a1/T;
    u(i,:)=a2/a1;
    o(i,:)=a3/a1-u(i,:).^2;
    if (o(i,:)<0.01)
     o(i,:)=0.01;
    end
    E(:,:,i)=diag(o(i,:));
  end
end