missing value in text file

Are you trying to do data pre-processing for subsequent data mining? Why matlab? You have to do it manually in order to detect and correct problems like missing data, incorrect data type, repeat data etc. You may want to engage the help of ms excel to speed up the task. Import the original text file into an excel sheet and use the excel facilities (search, replace, sort etc) to help you to manipulate and clean the data.

There are a number of ways to deal with missing value, one of them is to replace it with the average of all other available values if it is a number, or one of the major category if it is a categorical value.

Only after a proper data pre-processing, can you test the data in your matlab code.