I recently posted a question on one subject on the main R-help list  
but was
stymied in finding a response because the error with confint.nls that  
was occurring
on my Intel Mac could not be reproduced under linux.

(https://stat.ethz.ch/pipermail/r-help/2006-November/117733.html)

I finally came up with a solution to my initial problem that  
satisfied my needs

(https://stat.ethz.ch/pipermail/r-help/2006-November/117800.html)

but I tried my problem just now on a powerpc, and I don't get the  
error there.
So, the question is why is the Intel Mac producing this error?

I paste below the example from the Intel Mac and then from the powerpc

Intel Mac (this copied from the above listing on R-help)

####The data, again
dd
Lum	GL	Gun	mBl
0.15	0	rouge	0.09
0.07	15	rouge	0.01
0.1	31	rouge	0.04
0.19	47	rouge	0.13
0.4	63	rouge	0.34
0.73	79	rouge	0.67
1.2	95	rouge	1.14
1.85	111	rouge	1.79
2.91	127	rouge	2.85
3.74	143	rouge	3.68
5.08	159	rouge	5.02
6.43	175	rouge	6.37
8.06	191	rouge	8
9.84	207	rouge	9.78
12	223	rouge	11.94
14.2	239	rouge	14.14
16.6	255	rouge	16.54
0.1	0	vert	0.04
0.1	15	vert	0.04
0.17	31	vert	0.11
0.46	47	vert	0.4
1.08	63	vert	1.02
2.22	79	vert	2.16
3.74	95	vert	3.68
5.79	111	vert	5.73
8.36	127	vert	8.3
11.6	143	vert	11.54
15.4	159	vert	15.34
19.9	175	vert	19.84
24.6	191	vert	24.54
30.4	207	vert	30.34
36.1	223	vert	36.04
43	239	vert	42.94
49.9	255	vert	49.84
0.06	0	bleu	0
0.06	15	bleu	0
0.08	31	bleu	0.02
0.13	47	bleu	0.07
0.25	63	bleu	0.19
0.43	79	bleu	0.37
0.66	95	bleu	0.6
1.02	111	bleu	0.96
1.46	127	bleu	1.4
1.93	143	bleu	1.87
2.49	159	bleu	2.43
3.2	175	bleu	3.14
3.96	191	bleu	3.9
4.9	207	bleu	4.84
5.68	223	bleu	5.62
6.71	239	bleu	6.65
7.93	255	bleu	7.87

###For initial values - this time using plinear algorithm insted of  
optim
gg <- model.matrix(~-1 + Gun/GL, dd)[ , c(4:6)]
dd.plin <- nls(Lum ~ cbind(rep(1, 51), gg^gamm), data = dd,
				start = list(gamm = 2.4),
				alg = "plinear"
				)
B <- as.vector(coef(dd.plin))
st <-list(Blev = B[2], beta = B[3:5], gamm = B[1])


dd.nls <- nls(Lum ~ Blev + beta[Gun] * GL^gamm,
			data = dd, start = st
			)

###  Here is the error that I observe
confint(dd.nls)
Waiting for profiling to be done...
Error in prof$getProfile() : step factor 0.000488281 reduced below
'minFactor' of 0.000976562

R version 2.4.0 Patched (2006-11-16 r39921)
i386-apple-darwin8.8.1

locale:
C

attached base packages:
[1] "stats"     "graphics"  "grDevices" "utils"     "datasets"
[6] "methods"   "base"

other attached packages:
      MASS   lattice
  "7.2-29" "0.14-13"
(still get this problem with today's patched version, however)

and now from the powerpc, the relevant code

st <-list(Blev = B[2], beta = B[3:5], gamm = B[1])
dd.nls <- nls(Lum ~ Blev + beta[Gun] * GL^gamm,
			data = dd, start = st)
confint(dd.nls)
Waiting for profiling to be done...
             2.5%       97.5%
Blev  -0.1612492  0.02988387
beta1 16.4752317 17.00843251
beta2 50.2193167 50.81325840
beta3  7.8496610  8.39135292
gamm   2.4811018  2.54296647

R version 2.4.0 Patched (2006-11-24 r39989)
powerpc-apple-darwin8.8.0

locale:
en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] "stats"     "graphics"  "grDevices" "utils"     "datasets"   
"methods"
[7] "base"

other attached packages:
     MASS
"7.2-29"

The Intel is having problems with some of the control
parameter settings for nls but I don't know why.
I hope that I have supplied sufficient information
for my question.
I would be thankful for any light that could be shed
on it.


ken

--
Ken Knoblauch
Inserm U371
Institut Cellule Souche et Cerveau
Département Neurosciences Intégratives
18 avenue du Doyen Lépine
69500 Bron
France
http://www.lyon.inserm.fr/371/






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