I am trying to fit oral pharmacokinetic function using R nls. The function can be seen here:
我尝试了以下方法:
dat <- data.frame(
Time = c(10, 15, 20, 30, 40, 60, 90, 120, 180, 210, 240, 300, 360),
C_PO = c(0,0.28,0.55,1.2,2,1.95,1.85,1.6,
0.86,0.78,0.6,0.21,0.18))
plot(dat$C_PO ~ dat$Time, data = dat, log = "y")
fit <- nls(C_PO~ka*100* (exp(-k*Time) - exp(-ka*Time))/(v*(ka- k)),
data = dat,
start = list(ka = 0.09, k = 0.01, v = 50))
#> Error in nls(C_PO ~ ka * 100 * (exp(-k * Time) - exp(-ka * Time))/(v * : singular gradient
该代码试图根据浓度值拟合非线性模型C_PO
在一段时间内Time
。使用图形剥离方法计算初始值。然而,错误消息显示为“单一梯度”。如何解决这个问题?