Remove everything after a string in a data frame column with missing values

Question

I have a data frame resembling the extract below:

Observation Identifier   Value
Obs001      ABC_2001     54
Obs002      ABC_2002     -2
Obs003                       


        

Answer 1

You could try the below sub command to remove all the non-space characters from _ symbol.

sub("_\\S*", "", string)

Explanation:

• _ Matches a literal _ symbol.
• \S* Matches zero or more non-space characters.

OR

This would remove all the characters from _ symbol,

sub("_.*", "", string)

Explanation:

• _ Matches a literal _ symbol.
• .* Matches any character zero or more times.