search for: both01

Hi, imagine the following matrix/data.frame Letter Number a 1 a 1 b 1 b 0 c 0 c 1 d 0 d 0 If the numbers for two identical letters are also identical then I want to remove either the first or the second row of that letter. If for a letter the numbers are 1 and 0 I want to remove the row with the 0. That means if the code works I would and up with the following matrix/data.frame Letter