Trades don't take place on the blockchain, instead majority of bitcoin trading takes place on centralized exchanges. So instead of blockchain analysis you should ask a centralized exchange to give you access to their database so that you can analyze what everyone is doing. Obviously they won't do that.

What you see some people do (like the scam site known as whalealert) is looking at the transactions and whenever it suites their trading goals they release it as a whale selling or buying bitcoin. Obviously no-one can know what that transaction was. Even if you can say for sure that it was from or to an exchange you still can't know if it was a buy/sell.