"是" in your example just means (in English) = "is/am/definitely/positively", as a compact word to affirm an action. I would call it a particle- it implies your action is affirmative, so your sentence translates into "I (definitely) came in yesterday". (Some would say your example sounds strange, but I get where you are coming from.)
Now "的" is also a particle, but it implies ownership of something, quite different from "是". Say, 這是我的嗎？是的。(Is this mine? Yes, it is)
I've got another example here, hope it helps:
你是昨天到的嗎？ Did you arrive yesterday? 是的。Yes, I did.
Sometimes, there is no literal translation for some words in English into Chinese. If you need a bit more examples, let me know~ I'll try to pull out a few more.