Andreas Aschbacher asked about an -nl- error...
I captured his example and ran it through Stata 8.2
...it worked the first try:
. clear
. set obs 100
obs was 0, now 100
. gen x=uniform()
. gen y=3 +.75/(1+exp(-2*x-0.1))
. capture program drop nlexample
. program nlexample
1. version 8
2. if "`1'" == "?"{ // alt+0145 1 alt+0146 <=> for `1'
3. global S_1 "b c k A"
4. global k = 1
5. global A = 1
6. global b = 1
7. global c = 1
8. exit
9. }
10. replace `1'=$b +$c/(1+exp(-$A*x-$k)) // alt+0145 1 alt+0146 <=> for
`1'
11. end
. nl example y
(obs = 100)
Iteration 0: residual SS = 302.5628
Iteration 1: residual SS = 21.36867
Iteration 2: residual SS = 5.00826
Iteration 3: residual SS = .0934839
Iteration 4: residual SS = .0852592
Iteration 5: residual SS = .0519648
Iteration 6: residual SS = .03807
Iteration 7: residual SS = .0003895
Iteration 8: residual SS = 8.82e-08
Iteration 9: residual SS = 5.27e-13
Source | SS df MS Number of obs =
100
-------------+------------------------------ F( 3, 96) =
4.64e+13
Model | .63290202 3 .21096734 Prob > F =
0.0000
Residual | 4.3634e-13 96 4.5452e-15 R-squared =
1.0000
-------------+------------------------------ Adj R-squared =
1.0000
Total | .63290202 99 .00639295 Root MSE =
6.74e-08
Res. dev.
= -3022.766
(example)
----------------------------------------------------------------------------
--
y | Coef. Std. Err. t P>|t| [95% Conf.
Interval]
-------------+--------------------------------------------------------------
--
b | 3.000001 2.32e-06 . 0.000 2.999996
3.000005
c | .7499993 2.61e-06 . 0.000 .7499941
.7500044
k | .0999987 4.97e-06 . 0.000 .0999888
.1000086
A | 2.000002 4.82e-06 . 0.000 1.999992
2.000011
----------------------------------------------------------------------------
--
* Parameter b taken as constant term in model & ANOVA table
(SEs, P values, CIs, and correlations are asymptotic approximations)
.
end of do-file
I would suggest that Andreas shut down and restart Stata, as nothing appears
to be wrong in his example.
Tom Steichen
----- Original Message -----
From: "Andreas Aschbacher" <[email protected]>
To: <[email protected]>
Sent: Thursday, November 13, 2003 8:56 AM
Subject: st: nonlinearleastsquare
> Here is a brief description of my problem:
>
> I put all the following code into nlexample.do
> ~~~~~~~~~~~~~~~~
> clear
> set obs 100
> gen x=uniform()
> gen y=3 +.75/(1+exp(-2*x-0.1))
>
>
> capture program drop nlexample
> program nlexample
> version 8
> if "`1'" == "?"{ // alt+0145 1 alt+0146 <=> for
> `1'
>
> global S_1 "b c k A"
> global k = 1
> global A = 1
> global b = 1
> global c = 1
> exit
> }
> replace `1'=$b +$c/(1+exp(-$A*x-$k)) // alt+0145 1 alt+0146 <=>
> for `1'
>
> end
>
>
> nl example y
> ~~~~~~~~~~~~~~~~~~~~~~~
> at last I give :do nlexample: in command line- and I always get the
> error-message
> ::: invalid name - and I don't know why,
> my ambition is to make nonlinear-fit for z(d) = a1*exp(-((d-a2)/a3)^2) +
> a4*exp(-((d-a5)/a6)^2)
> with LevenbergMarquardt therefore I need this example above.
> Thank you for any help. andreas
>
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