[R] why two diff. se in nlsList?

[Tao Shi]

Hi list,

In the object returned by summary.nlsList, what's the difference between "coefficients" and "parameters"?  The have the same "Estimate", different se (therefore t value), but same p values.

R.2.8.0 on winxp with nlme_3.1-89

Thanks,

...Tao

+++++++++++++++++++++++++++++++++++++++++++++++++

> library(nlme)
> fm1 <- nlsList(uptake ~ SSasympOff(conc, Asym, lrc, c0),
   data = CO2, start = c(Asym = 30, lrc = -4.5, c0 = 52))

> summary(fm1)$para[,,1]
    Estimate Std. Error  t value     Pr(>|t|)
Qn1 38.13977  0.9911148 38.48169 1.991990e-06
Qn2 42.87169  1.0932089 39.21638 2.583953e-06
Qn3 44.22800  1.0241029 43.18706 1.809264e-07
Qc1 36.42874  1.1941594 30.50576 1.140085e-05
Qc3 40.68373  1.2480923 32.59673 1.424635e-04
Qc2 39.81950  1.0167249 39.16447 2.692304e-06
Mn3 28.48286  1.0624246 26.80930 1.066434e-06
Mn2 32.12827  1.0174826 31.57624 3.488786e-06
Mn1 34.08482  1.3400596 25.43530 4.199333e-06
Mc2 13.55519  1.0506404 12.90184 4.385886e-06
Mc3 18.53506  0.8363371 22.16219 1.461563e-06
Mc1 21.78723  1.4113318 15.43735 5.756870e-06

> summary(fm1)$coef[,,1]
    Estimate Std. Error  t value     Pr(>|t|)
Qn1 38.13977  0.9163882 41.61967 1.991990e-06
Qn2 42.87169  1.0994599 38.99341 2.583953e-06
Qn3 44.22800  0.5829894 75.86415 1.809264e-07
Qc1 36.42874  1.3556273 26.87224 1.140085e-05
Qc3 40.68373  2.8632576 14.20890 1.424635e-04
Qc2 39.81950  1.0317496 38.59415 2.692304e-06
Mn3 28.48286  0.5852408 48.66861 1.066434e-06
Mn2 32.12827  0.8883225 36.16735 3.488786e-06
Mn1 34.08482  0.9872439 34.52522 4.199333e-06
Mc2 13.55519  0.3969189 34.15104 4.385886e-06
Mc3 18.53506  0.4121147 44.97549 1.461563e-06
Mc1 21.78723  0.6830001 31.89930 5.756870e-06


_________________________________________________________________


ore_012009