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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