Hi! I'm working on a project rn and I need to calculate the mean for specific rows in a column for a hugeee dataset, but all the tutorials I've seen ask you to painstakingly type out the exact rows you need for calculations. That works for smaller datasets but mine has over 1000 rows and i'm NOT doing all that and i'm p sure there's a faster way to do it. I just need to calculate the mean oil price in 2023 for various countries. The countries aren't the problem, i just need a way to tell R to compute the mean for all the oil price values for 2023 specifically.