Closes #1966 address derive_vars_joined bugs #2050

Job	Run time
Render README	0s
Validation	0s
Documentation	0s
Check / (4.1)	5m 28s
Check / (4.2)	7m 12s
Check / (4.3)	6m 53s
Spelling / Get R version	1s
Code Style / Get R version	1s
Links / Validate Links	7s
Code Coverage / Get R version	2s
Lint / Get R version	1s
Man Pages / Get R version	1s
Code Style / Code Style	2m 52s
Man Pages / Roxygen	2m 23s
Spelling / Spellcheck	3m 19s
Lint / Lint	5m 55s
Code Coverage / Test Coverage	5m 22s
Code Coverage / Generate badge for coverage	3s
	39m 40s

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