Precise positioning of the R-wave of the QRS complex

 

index_max=[];
for i=1:length(index)
     test=[];
     index(i)
     test=(index(i)-3:index(i)+3);
     val=[data(test(1)),data(test(2)),data(test(3)),data(test(4)),data(test(5)),data(test(6)),data(test(7))]
     if  data(index(i))>=0
        [aa,bb]=max(val)
     end 
     if  data(index(i))<0
        [aa,bb]=min(val)
     end 
     
     index_max(i)=test(1)+bb-1;    
     
end