Running examples in ‘FlexParamCurve-Ex.R’ failed
The error most likely occurred in:

> base::assign(".ptime", proc.time(), pos = "CheckExEnv")
> ### Name: extraF.nls
> ### Title: Compare Two nls Models Using Extra Sum-of-Squares F-Tests
> ### Aliases: extraF.nls
> 
> ### ** Examples
> 
> 
> 
> #fit and compare two nested nls models (7 vs 8 parameter models)
> 
> 
>    #create list for fixed parameters
> 
> 
>    modpar(posneg.data$age, posneg.data$mass, pn.options = "myoptions") 
[1] modpar will attempt to parameterize your data using the following sequential procedures:
[1]   (1) Extract parameter estimates for 8-parameter double-Richards curve in nls
[1]   (2) Use getInitial to retrieve parameter estimates for 8-parameter double-Richards curve
[1]   (3) Extract parameter estimates for 4-parameter Richards curve in 
[1]   (4) Use getInitial to retrieve parameter estimates for 4-parameter Richards curve
[1] if any approaches are successful, modpar will return these and terminate at that stage
[1]  
[1] (1) Status of 8-parameter double-Richards curve fit in nls:
[1] ....8 parameter nls fit failed
[1] (2) Status of 8-parameter double-Richards getInitial call
[1] ....8-parameter getInitial successful
$Asym
[1] 4427.343

$K
[1] 0.07040843

$Infl
[1] 30.13159

$M
[1] 0.9867801

$RAsym
[1] -1136.717

$Rk
[1] 0.2112253

$Ri
[1] 108.0177

$RM
[1] 0.8085435

Warning messages:
1: In reorder(upper) :
  different names for ‘start’ and ‘upper’: not reordering to match
2: In reorder(upper) :
  different names for ‘start’ and ‘upper’: not reordering to match
3: In reorder(upper) :
  different names for ‘start’ and ‘upper’: not reordering to match
> 
> 
>    richardsR1.nls <- nls(mass ~ SSposnegRichards(age, Asym = Asym, K = K,
+ 
+ 
+    Infl = Infl, M = M, RAsym = RAsym, Rk = Rk, Ri = Ri, RM = RM, modno = 1, pn.options = myoptions)
+ 
+ 
+                         , data = posneg.data)
Error in nls(mass ~ SSposnegRichards(age, Asym = Asym, K = K, Infl = Infl,  : 
  singular gradient
In addition: Warning message:
In reorder(upper) :
  different names for ‘start’ and ‘upper’: not reordering to match
Execution halted
Examples with CPU (user + system) or elapsed time > 5s
                  user system elapsed
SSposnegRichards 4.962   0.01   6.551