[R] error in unique() command

Dear all, Good day! I have a question in my codes, would you please help me how to rectify it? these are my coded but at the last line I received the error! mac_30 = read.dta("MAC results4.dta") mac_30 map_30 = read.dta("MAP results4.dta") map_30 mac_30$weight = 1/nrow(mac_30) mac_30 map_30$weigh

[R] Appending many different and separate Excel files using R

data come from. As I have many Excel files and their sizes are very big I should write a loop in R to do the work. I will be very happy if you guide and help me to write the codes. Thank you very much in advance. Kind regards, Amir Kasaeian Amir Kasaeian, PhD Student in Biostatistics, Dept