The reason Ron might *appear* angry at first is because he's jealous of Harry. Harry has been chosen as a Triwizard Champion, something Ron desperately wants to be. Ron feels like he's constantly in Harry's shadow, and this just makes him feel worse.
He also feels like Harry is ignoring him, focusing more on his training and the Triwizard Tournament than on their friendship. This makes Ron feel insecure and left out.
However, it's important to remember that Ron cares deeply for Harry. He's not really angry, just hurt and a little insecure.
Here's how Ron's jealousy and insecurity play out in the story:
* He is initially excited for Harry, but as the tournament progresses, he becomes increasingly frustrated and jealous.
* He is constantly comparing himself to Harry, feeling inadequate and envious of Harry's success and popularity.
* He lashes out at Harry, both verbally and physically, but ultimately feels regretful for his actions.
* He eventually confesses his jealousy and insecurities to Harry, and they reconcile.
Overall, Ron's jealousy and insecurity are a major source of conflict in *Goblet of Fire*, but it's a conflict that ultimately strengthens their friendship.