Factor 因子

• 利用 factor 建立因子

• converting factor to date

DJIcsv[,1] <- as.Date(DJIcsv[,1], format = "%Y/%m/%d")

Reference:

• 因子 · R Basic

• R help converting factor to date

• R 字串與因子 - G. T. Wang
• R Factor - Learn the complete process from Creation to Modification! - DataFlair