How to refresh matrix on every iteration

Hello,

I am facing a problem in refreshing values on every iteration: I have the attached code, I want to refresh the values stored in the below array matrix on every change of p values (in other words, assign empty before every 'p' iteration). Currently if (isempty(HTDM)~=1) it is storing previous values which I infact shoud be no values be stored in the below array(s). Please help me, it would great help for me:

In third iteration (when p=3), the count shoud be zero, and data stored in below array(s) should be zero.

EndHist_CurHTD(:,m)=TrainsetAllEnd(:,j);
EndHist_PreHTD(:,m)=TrainsetAllEnd(:,j-1);
IndexHistCurHTD(m,1)=j;
IndexHistPreHTD(m,1)=j-1;
Count=nnz(IndexHistPreHTD);

Thanks again in advance, Pl help