getting an error message when using hmcSampler

Dear all,

I have this log-function on which I apply the hmcSampler:

T=1000;
g=randn(T,1);
u=randn(T,1);
k1=0.01;
k2=0.02;

for ii=1:T
logf=@(x)func(x,g, k1, k2,ii, u);
 smp = hmcSampler(logf,u(ii))
end

where

function  LL= func(x,y,k1,k2, t,u)
 u(t)=x; 
e2=(y-u).^2;
kk=- 0.5*x^2/k2;
  M=-.5*sum(e2)/k1;
LL=M+kk;
end

Then, I get this error

Error using
stats.mcmc.utils.InputValidator.validateLogPDFAndStartAnalyticalGradient (line
346)
Error in calling log posterior density with the specified starting point.

Error in stats.mcmc.HamiltonianSampler.processLogPDFAndStartAnalyticalGradient
(line 577)
                [~,~,isGradientRowVector] =
                stats.mcmc.utils.InputValidator.validateLogPDFAndStartAnalyticalGradient(logpdf,start');
                
Error in stats.mcmc.HamiltonianSampler (line 284)
                [logpdf,start] =
                stats.mcmc.HamiltonianSampler.processLogPDFAndStartAnalyticalGradient(logpdf,start);
                
Error in hmcSampler (line 99)
hmc = stats.mcmc.HamiltonianSampler(logpdf,start,varargin{:});

Error in Main_code (line 53)
 smp = hmcSampler(logf,u(ii))

Caused by:
    Error using func
    Too many output arguments.
 

I can not find what is causing this problem. "Too many output arguments."?

Any ideas,

Thanks a lot

[ektor]

any ideas please?