subset by multiple letters condition

You may investigate a solution based on regular expressions.

Some tutorials to help:

http://www.regular-expressions.info/rlanguage.html

http://www.endmemo.com/program/R/grep.php

http://biostat.mc.vanderbilt.edu/wiki/pub/Main/SvetlanaEdenRFiles/regExprTalk.pdf

https://rstudio-pubs-static.s3.amazonaws.com/74603_76cd14d5983f47408fdf0b323550b846.html

http://stat545.com/block022_regular-expression.html

https://www.youtube.com/watch?v=q8SzNKib5-4


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Best,

GG