mortality rate change at the first time point, bug fix

When I estimated the mortality rates from simulated network aging data, the first time points always have a very low value.  This abnormality bugged me because it contradicts the theoretic assumption on the initial stage, but I thought it is due to the boundary effect and did not investigate it for several weeks. Also, I thought there may be some differences between theoretical predictions and empirical data. I went over the code today and found out that it is due to typo in the code.  After correction, the initial stage of mortality rate change fit extremely well to the network aging model.
Lesson learned: I should be more confident about my theoretic models and should pay more attention to abnormality during numerical works.