Index Exceeds matrix dimensions error message in my Speech Segmentation code, would you help, please?

Hi, I am trying to segment a signal into its non-zero blocks. Below is the algorithm that I wrote to find the number of non-zero elements in each non-zero block of the signal. the vector Num is supposed to output these numbers. I get the error message: ??? Index exceeds matrix dimensions.

Error in ==> SegmentSignal at 56 if Numcount(j-1,1)==Numtimes

Please Help!

Thank you.

   flags =(NormEnergySigX>0.05);
   if flags(1)==0

    k=0;
    Num=[];
    Numtimes=0;
    Numcount=[];

    for j=1:length(flags)
        if (flags(Numtimes+1)==0)
            Numtimes=0;
        end

        if flags(j)==0
        Numtimes=Numtimes+1;
        Numcount(j,1)=(flags(j)==0)*Numtimes;
        end
        if flags(j)==1
        if Numcount(j-1,1)==Numtimes
            k=k+1;
            Num((Numcount(j-1,1)==Numtimes),k)=Numtimes;

        if flags(Numtimes+1)==1
            times=0;

        if flags(j)==1
            Numtimes=Numtimes+1;
            Numcount(j,1)=(flags(j)==1)*Numtimes;

        if Numcount(j-1,1)==Numtimes
            Num((Numcount(j-1,1)==Numtimes),k)=Numtimes;    % Num is supposed to contain the number of non-zero elements 
        % in each consecutive chunks of non-zero elements in flags. 
        end 
        end
        end
        end
        end
    end
   end

Answer 1

[Walter Roberson]

You do not create Numcount(j,1) unless flags(j) is 0, or unless flags(j) is 1 and a series of additional conditions all apply. If you were to encounter two locations in a row where the combination of those situations did not apply, then when you went to test Numcount(j-1,1) then that would not have been created yet so you would get the index out of range method.