I have a CSV of the following type:
code year sales
2011 1970 5000
2011 1971 5200
2011 1972 ...
...
2015 1970
2015 1971
2015 1972
...
3025
...
3026
...
3052
...
How can I select all the code lines starting with '20', or '30', and average sales year )?
Thank you so much !!