How to exchange rows and column of a matrix in mathcad prime 9

You are using the and() and or() functions. These functions are meant for image operations, accepting only matrices as their arguments:

, not to be used as (the) boolean functions you are using them:

For boolean operators, use the AND (˄) and OR (˅) operators from the operators tableau.

Success!
Luc

Some additional remarks:

• Statements like this have no effect! The error string is neither returned nor shown
  
• This statement (apart from using the wrong "and" as Luc already explained) sure is not what the task request and not what you want it to so
  

  In case of a wrong value of e, the "return" statement ends the program immediately and returns the string. But you need to collect ALL possible errors and return them each one in one line. So in case of errors your output could have up to five lines (not square, not symmetric, wrong e, row out of bound, column out of bound). So its necessary to collect all errors in a vector and return it only after the last possible error condition is checked.

  The return in the "else" branch would stop the program as well. So in case of a valid e value you get just the string as the result of your function and not the changed matrix as demanded. There is no need for this "else" anyway because in case of a valid e-value the program simply should do what it was written for - modifying the matrix.
• Using the row and column selectors which Prime provides can make dealing with whole columns or rows much easier than using loops