"it didn't recognize mean_trravel3 and the other variables after that why this happen "
Answer: Bad data design.
After those IF/ELSEIFs you have no easy way to know which of those variables you have created or not, so you have no easy way to process them. Your bad data design painted you into a corner, where you will either need to add some flags or write some ugly slow meta-programming to know which variables you created. Either way, it will add complexity and slow down your code.
Solution: Do not force meta-data (e.g. pseudo-indices) into variable names. Use actual indexing.
If you had simply stored the data in arrays using indexing you would not have this problem: the array(s) that you preallocated before the loop would always exist after the loop, togerther with any data that you add to it/them. Using arrays and indexing is how MATLAB works best. You should use arrays and indexing.
