Initial Margin File


I am trying to provide initial margin prediction for a multi classification problem in R. Just wondering what the correct format of margin file should be. I have created csv file (train.txt.base_margin) with each row representing the initial probability of each class of each instance. e.g., the first 2 rows (instance) of 4 classes would be
0.5, 0.3,0.1,0.1
I have not been successful so far.