Errors in running code in vignettes:
when running code in 'nlmrt-vignette.Rnw'

> options(width = 60)

> pastured <- data.frame(time = c(9, 14, 21, 28, 42, 
+     57, 63, 70, 79), yield = c(8.93, 10.8, 18.59, 22.33, 39.35, 
+     56.11, 61.73, 64.62, 67 .... [TRUNCATED] 

> regmod <- "yield ~ t1 - t2*exp(-exp(t3+t4*log(time)))"

> ones <- c(t1 = 1, t2 = 1, t3 = 1, t4 = 1)

> huetstart <- c(t1 = 70, t2 = 60, t3 = 0, t4 = 1)

> require(nlmrt)
Loading required package: nlmrt

> anmrt <- nlxb(regmod, start = ones, trace = FALSE, 
+     data = pastured)

> print(anmrt)
nlmrt class object: x 
residual sumsquares =  4648.1  on  9 observations
    after  3    Jacobian and  4 function evaluations
  name            coeff          SE       tstat      pval      gradient    JSingval   
t1               38.8378            NA         NA         NA  -3.039e-11           3  
t2               1.00007            NA         NA         NA  -7.748e-10   1.437e-09  
t3              0.998202            NA         NA         NA   1.889e-08   2.275e-16  
t4              0.996049            NA         NA         NA    4.15e-08   4.933e-26  

> anmrtx <- try(nlxb(regmod, start = huetstart, trace = FALSE, 
+     data = pastured))

> print(strwrap(anmrtx))
 [1] "c(0.480575683702448, 0.669264006079334,"              
 [2] "-2.28426563497325, 0.843862687207341,"                
 [3] "0.734652618487168, 0.0665106492947132,"               
 [4] "-0.985862291968445, -0.0250879549069225,"             
 [5] "0.500350456693326)"                                   
 [6] "c(1, 1, 1, 1, 1, 1, 1, 1, 1, -0.981556726091092,"     
 [7] "-0.948171282599527, -0.869750270888722,"              
 [8] "-0.758399834057036, -0.484261107837448,"              
 [9] "-0.223408951427337, -0.149363030476145,"              
[10] "-0.086933293312168, -0.0385258954067725,"             
[11] "1.12712321032759, 3.11275223693953, 7.48692917929397,"
[12] "12.9373484175607, 21.6609765596453, 20.654376815193," 
[13] "17.5183401160421, 13.0985419560081, 7.73883739451332,"
[14] "2.47654281941789, 8.21473160617155, 22.7941238760067,"
[15] "43.1098907467039, 80.9615739893344, 83.5067043689986,"
[16] "72.5808432835117, 55.6490931778844, 33.8144464340477)"
[17] "44"                                                   
[18] "32"                                                   
[19] "c(t1 = 69.9553722026374, t2 = 61.6818319271118, t3 =" 
[20] "-9.2088020481334, t4 = 2.37778402563407)"             
[21] "8.37588360361953"                                     
[22] "c(-Inf, -Inf, -Inf, -Inf)"                            
[23] "c(Inf, Inf, Inf, Inf)"                                
[24] "integer(0)"                                           

> anls <- try(nls(regmod, start = ones, trace = FALSE, 
+     data = pastured))
Error in nlsModel(formula, mf, start, wts, scaleOffset = scOff, nDcentral = nDcntr) : 
  singular gradient matrix at initial parameter estimates

> print(strwrap(anls))
[1] "Error in nlsModel(formula, mf, start, wts,"         
[2] "scaleOffset = scOff, nDcentral = nDcntr) : singular"
[3] "gradient matrix at initial parameter estimates"     

> anlsx <- try(nls(regmod, start = huetstart, trace = FALSE, 
+     data = pastured))
Error in nls(regmod, start = huetstart, trace = FALSE, data = pastured) : 
  singular gradient

> print(strwrap(anlsx))
[1] "Error in nls(regmod, start = huetstart, trace ="
[2] "FALSE, data = pastured) : singular gradient"    

> awnls <- wrapnls(regmod, start = ones, data = pastured, 
+     control = list(rofftest = FALSE))

> print(awnls)
Nonlinear regression model
  model: yield ~ t1 - t2 * exp(-exp(t3 + t4 * log(time)))
   data: data
   t1    t2    t3    t4 
69.96 61.68 -9.21  2.38 
 residual sum-of-squares: 8.38

Number of iterations to convergence: 0 
Achieved convergence tolerance: 7.15e-08

> cat("Note that the above is just the nls() summary result.\n")
Note that the above is just the nls() summary result.

> shobbs.res <- function(x) {
+     if (length(x) != 3) 
+         stop("hobbs.res -- parameter vector n!=3")
+     y <- c(5.308, 7.24, 9.638, 12.866, .... [TRUNCATED] 

> shobbs.jac <- function(x) {
+     jj <- matrix(0, 12, 3)
+     tt <- 1:12
+     yy <- exp(-0.1 * x[3] * tt)
+     zz <- 100/(1 + 10 * x[2] * yy)
+   .... [TRUNCATED] 

> st <- c(b1 = 1, b2 = 1, b3 = 1)

> ans1 <- nlfb(st, shobbs.res, shobbs.jac, trace = FALSE)

> print(ans1)
nlmrt class object: x 
residual sumsquares =  2.5873  on  12 observations
    after  10    Jacobian and  14 function evaluations
  name            coeff          SE       tstat      pval      gradient    JSingval   
b1               1.96186        0.1131      17.35  3.166e-08  -7.327e-06       130.1  
b2               4.90916        0.1688      29.08  3.282e-10   1.433e-07       6.165  
b3                3.1357       0.06863      45.69  5.768e-12   1.717e-06       2.735  

> cat("No jacobian function -- use internal approximation\n")
No jacobian function -- use internal approximation

> ans1n <- nlfb(st, shobbs.res, trace = FALSE, control = list(watch = FALSE))

> print(ans1n)
nlmrt class object: x 
residual sumsquares =  2.5873  on  12 observations
    after  10    Jacobian and  14 function evaluations
  name            coeff          SE       tstat      pval      gradient    JSingval   
b1               1.96186        0.1131      17.35  3.166e-08  -7.326e-06       130.1  
b2               4.90916        0.1688      29.08  3.282e-10   1.428e-07       6.165  
b3                3.1357       0.06863      45.69  5.768e-12   1.719e-06       2.735  

> shobbs.f <- function(x) {
+     res <- shobbs.res(x)
+     as.numeric(crossprod(res))
+ }

> shobbs.g <- function(x) {
+     res <- shobbs.res(x)
+     JJ <- shobbs.jac(x)
+     2 * as.vector(crossprod(JJ, res))
+ }

> require(optimx)
Loading required package: optimx
Warning in library(package, lib.loc = lib.loc, character.only = TRUE, logical.return = TRUE,  :
  there is no package called 'optimx'

> aopx <- optimx(st, shobbs.f, shobbs.g, control = list(all.methods = TRUE))

  When sourcing 'nlmrt-vignette.R':
Error: could not find function "optimx"
Execution halted

  'nlmrt-vignette.Rnw'... failed