[R] Problems using nlmrt package

Wed Jun 17 17:08:00 CEST 2015

Hello to everybody,

I want to implement a non-linear least square curve fitting and I am using
the package "nlmrt", concretely the function nlxb. I have a dataset with
three variables and 176 values, one response variables (R) and two
predicting variables (T and H). When I fit a model of the form R ~
a*b^((T-10)/10) to my data using the function nlxb seems to be all ok with
a complet output; the same happens when I fit a model R ~ a + b*H - c*H^2.
But due to my research interest, when I try to fit a model result of the
product of the above models (R ~ (b1*b2^((T-10)/10))*(b3 + b4*H - b5*H^2) I
do obtain NA values in the SE, tstat and pval fields from the nlxb output,
as showed below:

nlmrt class object: x
residual sumsquares =  25348  on  176 observations
    after  4    Jacobian and  5 function evaluations
  name            coeff          SE       tstat      pval
gradient    JSingval
R10            0.0619936            NA         NA         NA
7.494e-06        8822
Q10              2.27113            NA         NA         NA
5.422e-08       217.5
a                 133.85            NA         NA         NA
-2.288e-09       75.96
b                56.8145            NA         NA         NA
8.058e-09       0.658
c                1.11775            NA         NA         NA
2.8e-07   1.928e-15

I would like to know which error do you think I am making. Attached is the
document which contain the data.

Thank you very much in advance,

Carlos.

-- 
Carlos Ortiz Oñate

PhD student

Department of Agricultural Production

Technical University of Madrid

e-mail: ortiz.onate.carlos at gmail.com <teba at life.ku.dk>
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R	T	H
36.47	14.10	5.95
34.28	14.25	5.65
35.86	14.90	7.78
38.18	18.10	4.53
33.52	14.40	6.15
29.44	14.60	4.55
34.79	14.80	6.78
20.38	16.70	3.58
26.70	14.90	3.00
33.30	14.90	3.65
20.28	15.00	3.58
51.18	16.90	2.78
29.76	14.90	2.48
14.90	15.10	2.40
21.05	15.30	3.10
16.18	17.10	2.85
26.50	11.40	10.85
37.69	11.90	7.08
37.37	11.90	7.30
27.02	12.00	5.83
42.16	7.20	26.03
47.75	7.70	20.15
53.05	7.90	17.78
26.48	8.00	13.53
47.50	7.20	11.45
28.47	7.40	20.85
45.62	7.40	15.23
42.31	7.90	16.45
18.10	4.10	27.35
27.71	5.50	17.58
34.27	5.60	28.33
27.75	5.70	21.03
33.09	4.20	37.28
19.05	4.20	41.63
14.08	4.80	36.48
23.15	5.30	28.93
24.64	4.30	31.48
35.80	4.40	33.50
23.41	4.40	32.63
29.63	4.60	25.25
78.01	10.00	25.45
60.40	10.20	28.28
61.32	10.20	32.35
48.25	10.30	28.45
54.62	11.00	18.63
55.19	11.10	21.18
69.03	11.80	22.03
64.01	14.40	15.78
41.20	12.70	16.43
39.20	12.80	12.63
35.20	12.90	12.88
79.98	15.30	11.03
69.60	13.80	27.65
64.32	14.00	18.20
93.22	14.30	24.58
91.86	15.80	22.23
50.28	14.40	4.73
37.03	14.50	5.03
47.23	14.90	5.33
47.65	16.80	3.93
48.68	14.90	8.38
73.43	14.90	10.00
47.31	15.10	7.38
75.10	15.90	11.93
45.40	12.60	10.13
47.86	12.90	9.28
49.39	13.10	12.05
37.27	13.70	5.53
41.63	8.40	11.43
53.83	9.10	11.48
36.66	9.20	8.85
44.03	9.60	11.23
45.94	5.90	29.70
60.64	6.60	14.98
48.91	6.60	23.83
47.02	6.60	25.13
13.62	1.30	14.98
24.86	1.60	13.75
27.28	1.80	17.08
28.16	2.20	14.13
23.29	2.60	39.65
23.23	2.60	36.35
25.10	2.70	36.05
25.68	3.40	32.85
54.88	9.90	26.80
39.19	10.50	25.23
59.74	10.90	25.03
42.39	12.50	26.23
49.24	6.80	30.65
52.70	7.00	30.00
49.18	7.50	29.43
69.69	7.60	29.30
56.05	9.80	28.78
45.72	9.90	26.53
56.07	10.30	28.70
48.40	11.80	29.25
39.10	14.60	11.15
58.45	14.90	9.58
78.41	15.50	6.50
65.89	15.70	12.05
45.25	13.40	5.40
45.87	14.00	5.00
32.47	14.40	7.05
46.08	16.70	1.65
43.08	16.70	4.18
50.24	17.10	6.43
39.22	17.60	4.83
26.41	17.70	5.30
37.58	12.30	5.78
20.67	12.90	3.15
25.80	12.90	2.63
27.71	13.20	3.80
22.74	13.20	4.50
17.18	13.40	4.50
17.95	13.70	5.75
15.77	14.30	4.75
80.91	6.60	24.25
37.71	6.80	17.00
60.88	7.30	17.50
47.62	7.30	15.00
45.92	4.40	27.50
19.28	5.70	19.50
32.94	6.10	22.25
52.46	6.40	19.50
20.03	1.20	25.88
26.29	1.90	23.75
25.09	2.40	21.00
35.26	2.80	23.10
11.00	1.30	27.60
23.49	1.60	22.70
48.21	2.40	21.38
17.76	3.10	24.95
10.95	1.70	27.60
20.90	1.80	24.95
28.61	1.90	22.70
47.77	2.00	21.38
24.96	3.10	19.55
20.90	6.10	19.75
24.63	6.20	17.45
27.10	6.20	22.30
28.96	10.00	18.70
32.04	10.00	15.80
44.78	10.20	19.60
50.55	10.80	21.40
33.81	11.70	9.80
42.71	12.00	12.60
42.32	12.10	11.90
56.49	16.80	11.20
53.77	12.50	12.10
81.96	12.80	12.00
67.85	13.40	9.00
38.25	13.60	9.90
58.57	16.00	3.40
44.80	16.00	3.40
27.37	16.30	3.00
52.12	18.30	5.10
15.24	13.60	1.70
8.97	13.90	1.80
13.60	14.20	3.90
4.24	14.30	2.60
25.73	13.40	3.80
24.97	13.50	3.10
29.62	13.50	3.90
23.37	13.60	7.10
34.60	10.40	17.60
35.98	10.50	9.70
42.13	10.60	10.60
43.51	11.50	6.80
43.17	8.80	14.60
34.13	9.10	9.80
51.48	9.40	11.00
42.47	9.40	8.30
12.27	6.00	26.30
27.19	6.10	17.20
26.06	6.40	20.70
36.07	6.50	19.90