# [R] weighted 2 or 3 parameter weibull estimation?

Jeff D. Hamann jeff_hamann at hamanndonald.com
Fri Apr 5 09:19:25 CEST 2002

```  I've figured out how to use optim (barely) to estimate 2 parameter =
weibull distributions. I can't get over how easy this is. What I need to =
do is use a weight in the observations.....

For example,=20

the tree diameters and weights are are=20

4.70 , 100
6.00, 98
7.10,  75.0
8.10, 86.3
8.60, 80.456
8.90, 20.5
9.50, 16.6
11.40, 12.657
11.80, 12.47
14.50, 8.98
16.00,4.5
16.90,2.36
18.90, 0.256

which yield

LOCATION =3D   0.0000              MEAN =3D   10.9921
SCALE =3D  12.3436          VARIANCE =3D   18.0027
SHAPE =3D   2.8050          SKEWNESS =3D    0.2354

which are the values without the weights. I can't find any reference to =
weights in the optim function and I'm afraid I'm a little stuck here. =
After I figure out how to include the weights, I'll then need to =
estimate the 3-parameter estimates. Any help would be greatful.=20

Thanks,
Jeff.

Jeff D. Hamann
Hamann, Donald & Associates, Inc.
PO Box 1421
Corvallis, Oregon USA 97339-1421
Bus. 541-753-7333
Cell. 541-740-5988
jeff_hamann at hamanndonald.com
www.hamanndonald.com

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