[R] question with drm function in "drc package"

[li li]

Hi all,
  I am trying to use the drm function in drc package to fit a 4 PL or 3PL
curve for an assay response. Please see the listed data below. When I do
the curve fitting, it returns the following error message. Anyone who
familiar with this have any input on what went wrong?
   Thanks so much in advance!!
      Hanna

> dat
      values   log_dose
1   -68.1125  3.9120230
2   -73.8955  3.9120230
3   -75.1235  3.9120230
4   -47.3205  3.2188758
5   -52.9835  3.2188758
6   -58.0075  3.2188758
7     8.2515  2.5257286
8   -24.5925  2.5257286
9   -18.1425  2.5257286
10   75.3375  1.8325815
11   89.3755  1.8325815
12  115.9685  1.8325815
13  345.7675  1.1394343
14  470.8125  1.1394343
15  514.8985  1.1394343
16 1003.2235  0.4462871
17 1033.0345  0.4462871
18  866.1365  0.4462871
19 1383.6525 -0.2468601
20 1431.3245 -0.2468601
21 1459.8025 -0.2468601
22 1852.5795 -0.9400073
23 1917.8015 -0.9400073
24 1858.0875 -0.9400073
25 1995.1185 -1.6331544
26 2033.9455 -1.6331544
27 1991.0405 -1.6331544
28 2064.5855 -2.3263016
29 2043.5195 -2.3263016
30 2089.8525 -2.3263016
31 2147.8445 -3.0194488
32 2047.7905 -3.0194488
33 2002.5375 -3.0194488
34 2075.2665 -3.7125960
35 2068.3545 -3.7125960
36 2055.9605 -3.7125960
> mod1 <- drm(values~log_dose, fct=LL.4(), data=dat)
Error in optim(startVec, opfct, hessian = TRUE, method = optMethod, control
= list(maxit = maxIt,  :
  initial value in 'vmmin' is not finite
Error in drmOpt(opfct, opdfct1, startVecSc, optMethod, constrained,
warnVal,  :
  Convergence failed
>

	[[alternative HTML version deleted]]