我正在尝试使用 drc 包拟合四参数逻辑模型来绘制剂量反应曲线。代码如下所示。尝试拟合以下模型时出现错误，请指导我解决问题，谢谢！
optim 中的错误（startVec，opfct，hessian = TRUE，method = optMethod，control = list（maxit = maxIt，：由 optim 提供的非有限值 drmOpt 中的错误（opfct，opdfct1，startVecSc，optMethod，约束，warnVal，：收敛失败的
# growth inhibition = gi, concentration = conc
gi <- c("0", "5.24", "24.2","37.2", "71.9", "80","100", "100", "0", "0", "15.1", "42.8", "61.8", "73.5", "97.3", "100")
conc <- c("0", "100", "167", "278.89", "465.74", "777.79", "1298.91", "2169.19", "0", "100", "167", "278.89", "465.74", "777.79", "1298.91", "2169.19" )
df <- data.frame(conc, gi)
print(df)
library("MASS")
library("stats")
library("drc")
# Fit a log-logistic model (LL.4) with lower and upper asymptotic limits fixed at respectively 0 and 100
x <- drm(gi ~ conc, data = df, fct = LL.4(fixed = c(NA, 0, 100, NA)))```