I need to merg them into one data frame with 9 columns and (3x720) rows, where the first 3 rows in the final data frame is the first rows of each of the original data frames, and so forth for all rows in the original data frames.
You can create a new column in the data frames for the row number, then you merge them with a rbind and you order them based on the rn column that represents the row number in the original data frames. Note that the rbind will work only if the data frames have the same column names.
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