How can I stop farting because of a vegan diet?

Your stomach is probably not used to the huge amounts of fiber you are introducing to it. Humans have the weakest digestive systems of any species out there. Through many generations we have become accustomed to having at least half of our digestion done outside of our bodies by cooking. It is a natural consequence of being a recent convert. I'm sure that's less common in those who have been on raw food diets longer than you have. Perhaps you can phase in the raw more gradually rather than plunging in all at one. I admit to not eating as much vegetables as I should, and tend to gas really hard when I introduce more raw plant matter suddenly.