coding improvement for huge data

hello

I need to improve this code please, any idea !

a =donne_basic(:,colper); % before filteration unv = unique(a); % unique sorted values of alias/filtred occurance = [unv histc(a,unv)]; % count occurrences lP =length(a) ; % size of pure matrix l =length(unv); % size of filtered alias vector/filtered moyenne=zeros(l,2); deltta =zeros(l,2); time=zeros(lP,2); for i =1:l name =unv(i); for j=1:lP if(donne_basic(j,colper)==name) time(j)=donne_basic(j,1); end end if (occurance(i)==1) deltaV=0; moy =0; else V1 =time(1:end-1); V2 =time(2:end); deltaV =V2-V1; % les pas de temps delta_t ss =sum(deltaV); moy =(ss/occurance(i)); % les pas de temps delta_t end

thanks in advance

suhad