I found a good tip from the matlab community to find out the built-in function in Matlab. You can edit and change it. The tip as follows:
% You can use the [which] command to find the path name to the
% built-in function in question, i.e. -
% then point Matlab to that folder on your computer so that
% the fft.m file is in your "current folder" window. Then use
% the  command to edit the function, i.e. -
% The code for the fft function will appear in the editor window.
% Often it is useful to make small changes to the built-in code
% then comment out the changes as soon as you're done so that
% Matlab will continue to function as designed.
Fig. 1: Summary of PhD. process
I would like to share some good general questions for PhD viva. Useful for PhD candidates and also for examiners. Credit to my main supervisor who forward this information.
- What is original or novel about your work/thesis?
- What are the main issues / debates in your subject area? What is the current state of the art in your field?
- What were the crucial research decisions that you made? How did they impact what you did?
- How have you analysed/evaluated your work?
- Why have you tackled the problem in this way? What alternatives did you consider?
- What do your results mean? Are there longer term implications for industry?
- How could you improve your work/thesis?
- What had not been done on this topic/field before?
- What theories or models or analytical techniques did you use?
- Are the techniques you have used appropriate for this topic?
- What are the theoretical basis/underpinnings to your work?
- How long do you expect your work to remain innovative? How do you expect the field to develop in the next 5-10 years?
- What sets your work apart from others? Who are the leading researchers in your field?
- What issues arose during this work? How did you resolve any issues which arose in the course of your research?
- What have you learned from the process of doing a PhD? How will you apply what you have learnt in your future career?
- How did you deal with the practical/fieldwork aspect of your study?
- Do you think that your recommendations are appropriate or widely applicable?
- Is there scope for further study on this topic? What would you recommend the next student on this topic to do?
- Do your contributions have a limited timescale? When do you think your work will be obsolete?
- What have you done that merits the award of a PhD?