@tomleslie Thank you so much for your kind explantion and your effort to understand my poor English.

@tomleslie  The code was not mine but from the book which was published in 2002 year (Unfortunately I do not have a choice because my prof chose this book for the course which I am taking now.) and  I was trying to change it to modern version to study Stochastic process (with SDE) and Maple which I am not familiar with). But thank you so much for the explanations.

@tomleslie I am a very beginner in using Maple. How can I see the actual number like (1) ? not this :[column](4, [` 1 x 14 `*Matrix, `Data Type: `*anything, `Storage: `*rectangular, `Order: `*Fortran_order]) . Thank you!

@Thomas Richard Thank you ao much for good advice. I am using an old textbook so the codes in that book are very very old and I am an real beginner for Maple. I was wondering where I had to look up to find the changes (like LinearAlgebraMigration.) Thank you. 

 @Carl Love Thank you so much!! I do really learn a lot from this site because of people like you. Thank you so much!!

@acer step := trunc(stats[random, PA](1))-2 can be wriiten in modern version? Or it should be like that? I know what the code is doing but I do not understand stats[..] - I know the code generates random number 1,2 or 3 with probability vector PA and generates only one number but I don't know what stats[] is. Thank you again.

@acer Thank you so much!! I wrote the code using old version commands( like evalm ,&*) as you suggested and it worked, but I have learned a lot about recent version Maple  from your code and your explanation. Thank you so much!

@acer Thank you so much for the explanation. I will try it. Thank you so so much!! 

@acer Thank you so much! I am actually using Maple 2017 but I am studying the book "From elementary probability to stochastic differential equations with Maple -  year 2002" and trying to understand the code from the book since I have never used Maple before. So is the task done using cat() in the recent version ( Does not the Maple require making the list which can hold the matrix?)

@acer Thank you for the kind example. It helped me understand the difference!

Stupid me! I will be more careful.

@acer Thank you!! I saw your code (randomWalk ac.mw) now. Sorry for not choosing your answer as the best. This is my first time using this site. But thank you so much for the help.

Thank you!! 

@ThU It worked .What is the difference between else if and elif?