for i=1:num_k
    low=d_min+(i-1)*lamda_40;
    up=low+lamda_40;
    res=0;
    len=0;
    while(index<=length(XY))
    if((D_Y(index,1)>=low)&&(D_Y(index,1)<up))
          res=res+D_Y(index,2);
          index=index+1;
          len=len+1;
    else
        res=res/len;
        for j=(index-len):(index-1)
            D_Y(j,2)=res;
        end
        break;
    end
    end
end
请解释上述代码