Closes #2042 fix compute_dtf bug #2109

Job	Run time
Render README	0s
Documentation	0s
Validation	0s
Spelling / Get R version	1s
Check / (4.1)	6m 46s
Check / (4.2)	7m 45s
Check / (4.3)	6m 10s
Code Coverage / Get R version	1s
Links / Validate Links	6s
Lint / Get R version	2s
Man Pages / Get R version	1s
Code Style / Get R version	1s
Spelling / Spellcheck	2m 49s
Code Coverage / Test Coverage	5m 16s
Code Style / Code Style	3m 4s
Man Pages / Roxygen	2m 18s
Lint / Lint	6m 35s
Code Coverage / Generate badge for coverage	3s
	40m 58s

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