Hi Chuanjung,
I understand that you need help to preprocess 
to 
using the preprocessing function proposed in the paper. You can follow the following steps to achieve the same:
to using the preprocessing function proposed in the paper. You can follow the following steps to achieve the same:1) Define a function say “my_preprocessing”, that takes 
as input and returns 
as an output using the equation given in the research paper.
as input and returns as an output using the equation given in the research paper.2) Use “finverse” function given in MATLAB to find the inverse of the function “my_processing”. You can refer to below MathWorks documentation to understand more about the “finverse” function.
3) Use the inverse function obtained in step 2 to preprocess 
to 
.
to .I hope this helps.
