A similar question was posed quite a while back, without much specificity. The only answer identifies the taxing nature of a SEDE query on the server in order to get a rough estimate of the user reputation over time. This is rough because it doesn't include any reputation corrections (due to daily reputation cap and possible serial voting reversals).
Ideally it would be another table,
UserReputation(id, userid, creationdate, reputation) (say), representing the
reputation for the
creationdate (just a day stamp, like the votes)... a tabulation of the reputation tab that is already visible (to everyone) in your user profile:
Apparently there's a
RepHistory table available (internally):
If the daily reputation become to questionable in terms of anonymity-loss (for downvotes, say), perhaps the weekly, monthly, quarterly and yearly reputation league results would be a consolation prize.