function vm=blokaverage(a,long_bolk)
% programme d'alex ALLOU

for i=1:long_bolk
       vm(i)=mean(a(1:(long_bolk*2)));
   end
   
   for i=(long_bolk+1):(length(a)-(long_bolk+1))
       vm(i)=mean(a((i-long_bolk):(i+long_bolk)));
   end
   
   for i=(length(a)-long_bolk):length(a)
     vm(i)=mean(a((length(a)-long_bolk):length(a)));
 end
 
 vm=vm'