I have a CSV file. It is ordered by an identifier the first field. The identifier in the first field can appear in either 1 or in 2 lines in the field. I want to remove all lines in the file where the identifier only occurs once.
Example, file contains:
Id1,x11,x12... Id2,x21,x22... Id2,x23,x24...
In this case, I want to remove the first line because Id1 only occurs once.