I fetch daily historical Bitcoin price data, which gives me one data point per day with four columns: "open", "close", "min", and "max".
Now I'm comparing my historical Bitcoin purchases against these values for each date when I bought each any Bitcoin.
I currently use the "close" value, but is this the most sensible? I have thought about this a lot, but cannot figure out which one is the best.
Since there is only one data point per day, I cannot grab the exact market price for the very hour/minute/second when I bought.
I'm trying to get the "most correct" market price for the "whole day" when I made each Bitcoin purchase, in order to be able to calculate a "percentage difference" and see how smart/dumb I was for each purchase. After all, sometimes it differed a lot depending on which hour and even minute/second of that 24-hour period you actually "pressed the button".
(I made all my purchases P2P via Bisq and bank transfers, so each purchase could take up to a week in total, but I'm talking about when it was "set in stone" which occurred when both parties accepted/locked in the trade before payment was made.)