Consider the hafu dataset. In the Father and Mother columns, some values have question marks after the country name, indicating that the author was uncertain about the nationality of the parent:

 

   Year                   Series               Character Gender        Father    Mother  Eyes  Hair
1  1963           Yuki no Taiyou                   Sanae      F      Japanese  American            
2  1964               Cyborg 009           Joe Shimamura      M      American  Japanese brown brown
3  1967                Lupin III               Lupin III      M       French? Japanese? black black
4  1967             Nekome Kozou            Cat-Eyed Boy      M      Japanese   Fantasy brown      
5  1972                Gatchaman            Jun the Swan      F                         green green
6  1974           Great Mazinger                Jun Hono      F      American  Japanese black black
7  1975        Ichigo Monogatari                  Ichigo      F Scandinavian? Japanese? brown brown
8  1976 Kochira Katsushika-ku... Reiko Katherine Akimoto      F     Japanese?   French?  blue blond
9  1977     Haikara-san ga Tooru         Shinobu Iijyuin      M      Japanese    German  blue blond
10 1979       Mobile Suit Gundam               Amuro Ray      M      Japanese  Canadian  blue brown

 

Create two vectors FatherUncertain and MotherUncertain denoting whether or not there was a question mark in the Father or Mother column, respectively.

(from: Cotton, 2013, Learning R, O’Reilly)