The file values have been split by month.
You will need to remove the header from each file, except the first one.
Note: in the original file, entries are listed starting at the end of the year, so you must process all files from "december.csv" to "january.csv".
Use the "sed" command to delete the line starting with "Date" in each file, except the first one.
Use the "cat" command to concatenate all the files into one.
Use the following commands:
$ for csvfile in november.csv october.csv september.csv august.csv july.csv june.csv may.csv april.csv march.csv february.csv january.csv ; do sed -i /^Date/d $csvfile ; done
$ cat december.csv november.csv october.csv september.csv august.csv july.csv june.csv may.csv april.csv march.csv february.csv january.csv > data.csv
$ rm -f december.csv november.csv october.csv september.csv august.csv july.csv june.csv may.csv april.csv march.csv february.csv january.csv
It's possible to process the files the other way around. Start by concatenating all files (using the second command presented above) then remove all extra headers except the first one with the following "sed" command:
$ sed '1!{/^Date/d;}' data.csv