MATLAB: ‘too many input arguments’ in mhsample

input argumentsmhsampleStatistics and Machine Learning Toolbox

I am having the error 'too many input arguments' during my function call which itself is called by another built-in MatLab function 'mhsample'. I have not been able to figure out any reason for this error. Following is the snippet of the code:
% specification of unnormalized posterior pdf to sample from
 pdfPost=@(x)posteriorDist(x,C,artificialNetwork,xPrior);
% specification of proposal distribution
  pdfProp=@(x)priorDist(x,xPrior);
% specification of random number generator from proposal distribution
  generator = @(x) (xPrior(:,1)+rand(7,1).*(xPrior(:,2)-xPrior(:,1)));
% calculation of posterior of model parameters (lambda)
smpl = mhsample(x0,nsamples,'pdf',pdfPost,'proppdf',pdfProp,'proprnd',generator);
Following is the error message:
 Error using mhsample (line 117)
Error occurred while trying to evaluate the user-supplied
proppdf function '@(x)priorDist(x,xPrior)'.
 Error in metroPolisHastingSampling (line 33)
smpl =
mhsample(x0,nsamples,'pdf',pdfPost,'proppdf',pdfProp,'proprnd',generator);
 Caused by:
    Error using @(x)priorDist(x,xPrior)
    Too many input arguments.
'metroPolisHastingSampling' is the name of the script I have used for implementing Metropolis-Hastings sampling method.
So, the error is in proposal distribution which only has one input argument? So, why am I getting this error? Any useful comment is appreciated?
The code for priorDist is as follows:
 function [p] = priorDist(x,xprior)
      p=1/prod(xPrior(:,2)-xPrior(:,1));
 end
I have provided all other codes below: Here is the code for 'PosteriorDist':
 function ptr = posteriorDist(x,C,artificialNetwork)
 lh=likelihoodPost(artificialNetwork,x,C); % likelihood of observation given these parameters
 priorParam = priorDist(x); % computation of joint prior of model parameters
 ptr=lh*priorParam; % computation of unnormalized posterior
 end
rest of the definitions are
 x0=5*ones(7,1);
 nsamples=10000;
 xprior=[zeros(7,1) 15*ones(15,1)];
 C=rand(7,7);
I have taken a random just for testing purposes. artificialNetwork contains information and relevant data.

Best Answer

https://www.mathworks.com/help/stats/mhsample.html
"proppdf takes two arguments as inputs with the same type and size as start."
"The proposal distribution q(x,y) gives the probability density for choosing x as the next point when y is the current point. It is sometimes written as q(x|y)."
Your line
    pdfProp=@(x)priorDist(x,xPrior);
should probably just be
    pdfProp = @priorDist;
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