R Under development (unstable) (2024-09-10 r87115 ucrt) -- "Unsuffered Consequences"
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> options(digits = 4)
> suppressWarnings(RNGversion("3.5.0"))
> 
> ## package and data
> library("betareg")
> data("ReadingSkills", package = "betareg")
> 
> ## augment with random noise
> set.seed(1071)
> n <- nrow(ReadingSkills)
> ReadingSkills$x1 <- rnorm(n)
> ReadingSkills$x2 <- runif(n)
> ReadingSkills$x3 <- factor(sample(0:1, n, replace = TRUE))
> 
> ## fit beta regression tree
> rs_tree <- betatree(accuracy ~ iq | iq, ~ dyslexia + x1 + x2 + x3,
+   data = ReadingSkills, minsize = 10)
> 
> ## methods
> print(rs_tree)
Beta regression tree

Model formula:
accuracy ~ iq + iq | dyslexia + x1 + x2 + x3

Fitted party:
[1] root
|   [2] dyslexia in no: n = 25
|             (Intercept)                iq (phi)_(Intercept)          (phi)_iq 
|                   1.657             1.466             1.273             2.048 
|   [3] dyslexia in yes: n = 19
|             (Intercept)                iq (phi)_(Intercept)          (phi)_iq 
|                 0.38093          -0.08623           4.80766           0.82603 

Number of inner nodes:    1
Number of terminal nodes: 2
Number of parameters per node: 4
Objective function (negative log-likelihood): -66.73
> ## IGNORE_RDIFF_BEGIN
> summary(rs_tree) ## possibly small deviations in number of BFGS/Fisher iterations
$`2`

Call:
betatree(formula = accuracy ~ iq | iq, data = ReadingSkills)

Quantile residuals:
   Min     1Q Median     3Q    Max 
-2.495 -0.437  0.210  0.953  1.090 

Coefficients (mean model with logit link):
            Estimate Std. Error z value Pr(>|z|)    
(Intercept)    1.657      0.286    5.78  7.3e-09 ***
iq             1.466      0.248    5.92  3.2e-09 ***

Phi coefficients (precision model with log link):
            Estimate Std. Error z value Pr(>|z|)    
(Intercept)    1.273      0.307    4.15  3.4e-05 ***
iq             2.048      0.331    6.19  5.9e-10 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 

Type of estimator: ML (maximum likelihood)
Log-likelihood: 39.4 on 4 Df
Pseudo R-squared: 0.149
Number of iterations: 17 (BFGS) + 2 (Fisher scoring) 

$`3`

Call:
betatree(formula = accuracy ~ iq | iq, data = ReadingSkills)

Quantile residuals:
   Min     1Q Median     3Q    Max 
-2.426 -0.631 -0.067  0.778  1.555 

Coefficients (mean model with logit link):
            Estimate Std. Error z value Pr(>|z|)    
(Intercept)   0.3809     0.0486    7.83  4.8e-15 ***
iq           -0.0862     0.0549   -1.57     0.12    

Phi coefficients (precision model with log link):
            Estimate Std. Error z value Pr(>|z|)    
(Intercept)    4.808      0.414   11.61   <2e-16 ***
iq             0.826      0.395    2.09    0.036 *  
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1 

Type of estimator: ML (maximum likelihood)
Log-likelihood: 27.3 on 4 Df
Pseudo R-squared: 0.0391
Number of iterations: 16 (BFGS) + 2 (Fisher scoring) 

> ## IGNORE_RDIFF_END
> coef(rs_tree)
  (Intercept)       iq (phi)_(Intercept) (phi)_iq
2      1.6565  1.46571             1.273    2.048
3      0.3809 -0.08623             4.808    0.826
> if(require("strucchange")) sctest(rs_tree)
Loading required package: strucchange
Loading required package: zoo

Attaching package: 'zoo'

The following objects are masked from 'package:base':

    as.Date, as.Date.numeric

Loading required package: sandwich
$`1`
           dyslexia     x1     x2     x3
statistic 2.269e+01 8.5251 5.5699 3.6273
p.value   5.848e-04 0.9095 0.9987 0.9142

$`2`
          dyslexia     x1     x2     x3
statistic        0 6.4116 4.5170 8.2019
p.value         NA 0.8412 0.9752 0.2326

$`3`
NULL

> 
> proc.time()
   user  system elapsed 
   1.18    0.17    1.34