FIT OF THE TREE DATA BY GLS 
 
 
OLS estimate  18.86469 22.97248 0.12472 0.067716 1.831443 
 
 
Iteration  1 
GLS estimate of beta  19.39199 22.26495 0.112728 0.075035 1.810283 
 
Iteration  2 
GLS estimate of beta  19.41486 22.28658 0.112873 0.075275 1.815693 
 
Iteration  3 
GLS estimate of beta  19.41621 22.28601 0.112842 0.075272 1.815551 
 
Iteration  4 
GLS estimate of beta  19.41627 22.28603 0.112841 0.075272 1.815556 
 
Iteration  5 
GLS estimate of beta  19.41627 22.28603 0.112841 0.075272 1.815556 
 
Iteration  6 
GLS estimate of beta  19.41627 22.28603 0.112841 0.075272 1.815556 
 
Iteration  7 
GLS estimate of beta  19.41627 22.28603 0.112841 0.075272 1.815556 
 
Iteration  8 
GLS estimate of beta  19.41627 22.28603 0.112841 0.075272 1.815556 
 
Iteration  9 
GLS estimate of beta  19.41627 22.28603 0.112841 0.075272 1.815556 
 
Iteration  10 
GLS estimate of beta  19.41627 22.28603 0.112841 0.075272 1.815556 
 
Final estimate of sigma  0.065025 
 

Formula: ywt ~ weightfunc(x, delta, b10, b11, b20, b21, b3, wt)

Parameters:
    Estimate Std. Error t value Pr(>|t|)    
b10 19.41627    0.71168  27.282  < 2e-16 ***
b11 22.28603    0.91433  24.374  < 2e-16 ***
b20  0.11284    0.01820   6.202 1.25e-06 ***
b21  0.07527    0.01800   4.183 0.000273 ***
b3   1.81556    0.15986  11.357 8.66e-12 ***
---
Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 

Residual standard error: 0.06502 on 27 degrees of freedom

Number of iterations to convergence: 5 
Achieved convergence tolerance: 9.283e-07