Within the 'Importing data' section, regarding the second line of code "xts(dat, order.by = as.Date(rownames(dat), "%m/%d/%Y"))". I have entered that into code, but am greeted with the error message : 'order.by' cannot contain 'NA', 'NaN' OR 'Inf'. I assume it is picking up the 'na' in 'rownames'. How can I get around this issue?