I have an issue with my database.
I have 50 csv files which contain: date, price
I used : sp500_monthly <- list.files("my directory") to merge all the 50 files in one. But it does not seems to work since when I try to do, for exemple: mean(sp500_monthly$price), I have the following error : "Error in sp500_monthly$price : $ operator is invalid for atomic vectors".
My question is: how can I do to display, mean, standard deviation, etcetera?
Thank you very much!