" I have multiple .txt files, and each one has 30 rows and 1 column. "
First you need the paths or the file names to each text file. If you don't have a variable that stores this list, you can use dir() to list the content of directories and then you can sort out which files to read. There are lots of answers in this forum showing how to do that.
Then use readmatrix() to read in each text file within a loop. Since the files are not large, you can store them all in an array.
"I would like to calculate the mean of each row of all .txt files"
Your question states that the text files are "each one has 30 rows and 1 column" so what do you mean by calculating the mean of each row? By that definition, each row only has 1 value. Assuming the description is a mistake, once you read the data in you can use mean(A,2) to compute the mean across rows of "A".
If you have any questions or problems, leave a comment including your updated code and I'd be happy to get you unstuck.
