Calculation of Pfr:Ptot ratio for Type I Phytochrome from red:far-red photon ratio. "Exact" only for dichromatic irradiation, only approximate for R:FR ratio calculated from a broadband light source.
References
Mancinelli, A.L. (1994) The physiology of phytochrome action. In Photomorphogenesis in plants, 2nd edition. R.E. Kendrick and G.H.M. Kronenberg, eds. Kluwer Academic Publishers, Dordrecht, pp. 211-269. ISBN 978-0-7923-2551-2 (print), 978-94-011-1884-2 (on-line). doi:10.1007/978-94-011-1884-2_10
Examples
Pfr_Ptot_R_FR(1.15)
#> [1] 0.6919699
Pfr_Ptot_R_FR(0.10)
#> [1] 0.2305068
Pfr_Ptot_R_FR(c(0.1,1.15,5.0,20.0))
#> [1] 0.2305068 0.6919699 0.8209344 0.8569228