drc:：optim 'vmmin‘中的初始值不是有限的

Question

我想将log-logistic回归拟合到drc R package中的以下数据。但是，我的代码抛出了以下错误。

df1 <-
  structure(list(Temp = c(15L, 15L, 15L, 15L, 15L, 15L, 15L, 15L, 
      15L, 20L, 20L, 20L, 20L, 20L, 20L, 25L, 25L, 25L, 25L, 30L, 30L, 
      30L, 30L, 35L, 35L, 35L, 35L, 40L, 40L, 40L, 40L), Start = c(0L, 
      24L, 48L, 72L, 96L, 120L, 144L, 168L, 192L, 0L, 24L, 48L, 72L, 
      96L, 120L, 0L, 24L, 48L, 72L, 0L, 24L, 48L, 72L, 0L, 24L, 48L, 
      72L, 0L, 24L, 48L, 72L), End = c(24, 48, 72, 96, 120, 144, 168, 
      192, Inf, 24, 48, 72, 96, 120, Inf, 24, 48, 72, 96, 24, 48, 72, 
      Inf, 24, 48, 72, Inf, 24, 48, 72, Inf), Germinated = c(0L, 0L, 
      1L, 3L, 3L, 12L, 14L, 12L, 15L, 0L, 11L, 27L, 15L, 3L, 4L, 2L, 
      30L, 15L, 13L, 6L, 43L, 7L, 4L, 5L, 48L, 3L, 4L, 0L, 31L, 21L, 
      8L)), .Names = c("Temp", "Start", "End", "Germinated"), row.names = c(NA, 
      -31L), class = "data.frame")

library(drc)

fm1 <-
  drm(
        formula = Germinated ~ Start + End 
      , data    = df1
      , fct     = LL.2()
      , type    = "event" 
      , control   = drmc(
                            constr      = FALSE
                            , errorm      = TRUE
                            , maxIt       = 1500
                            , method      = "BFGS"
                            , noMessage   = FALSE
                            , relTol      = 1e-07
                            , rmNA        = FALSE
                            , useD        = FALSE
                            , trace       = FALSE
                            , otrace      = FALSE
                            , warnVal     = -1
                            , dscaleThres = 1e-15
                            , rscaleThres = 1e-15
                            )

          )

summary(fm1)