Many thanks HanOostdijk for your help. Actually, your suggestion provided me with a partial solution. I succeeded in converting the xlsx file into a data.frame one, using the following
my_data <- read_excel("QQQ.xlsx")
However, when applying
as.xts(read.table (my_data))
I got the following error
Error in read.table(my_data) :
'file' must be a character string or connection.
Any help would be appreciated