---
title: "Summary of Model Parameters"
output: 
  github_document:
    toc: true
    fig_width: 10.08
    fig_height: 6
  rmarkdown::html_vignette:
    toc: true
    fig_width: 10.08
    fig_height: 6
tags: [r, parameters, variable selection, feature selection]
vignette: >
  %\VignetteIndexEntry{Summary of Model Parameters}
  \usepackage[utf8]{inputenc}
  %\VignetteEngine{knitr::rmarkdown}
editor_options: 
  chunk_output_type: console
bibliography: bibliography.bib
---

```{r message=FALSE, warning=FALSE, include=FALSE}
library(knitr)
options(knitr.kable.NA = '')
options(digits = 2)
knitr::opts_chunk$set(comment = "#>")

if (!requireNamespace("dplyr", quietly = TRUE) ||
    !requireNamespace("BayesFactor", quietly = TRUE) ||
    !requireNamespace("lme4", quietly = TRUE) ||
    !requireNamespace("metafor", quietly = TRUE) ||
    !requireNamespace("lavaan", quietly = TRUE) ||
    !requireNamespace("brms", quietly = TRUE) ||
    !requireNamespace("psych", quietly = TRUE) ||
    !requireNamespace("rstanarm", quietly = TRUE) ||
    !requireNamespace("FactoMineR", quietly = TRUE)) {
  knitr::opts_chunk$set(eval = FALSE)
} else {
  library(parameters)
  library(dplyr)
}

set.seed(333)
```

The `model_parameters()` function (also accessible via the shortcut `parameters()`) allows you to extract the parameters and their characteristics from various models in a consistent way. It can be considered as a lightweight alternative to [`broom::tidy()`](https://github.com/tidymodels/broom), with some notable differences: 

- The names of the returned data frame are **specific** to their content. For instance, the column containing the statistic is named following the statistic name, i.e., *t*, *z*, etc., instead of a generic name such as *statistic* (**however**, you can get standardized (generic) column names using [`standardize_names()`](https://easystats.github.io/parameters/reference/standardize_names.html)).
- It is able to compute or extract indices not available by default, such as ***p*-values**, **CIs**, etc.
- It includes **feature engineering** capabilities, including parameters [**bootstrapping**](https://easystats.github.io/parameters/articles/bootstrapping.html).


## Correlations and *t*-tests

### Frequentist

```{r, warning=FALSE, message=FALSE}
cor.test(iris$Sepal.Length, iris$Sepal.Width) %>% 
  parameters()
```

```{r, warning=FALSE, message=FALSE}
t.test(mpg ~ vs, data = mtcars) %>% 
  parameters()
```


### Bayesian

```{r, warning=FALSE, message=FALSE}
library(BayesFactor)

BayesFactor::correlationBF(iris$Sepal.Length, iris$Sepal.Width) %>% 
  parameters()
```

```{r, warning=FALSE, message=FALSE}
BayesFactor::ttestBF(formula = mpg ~ vs, data = mtcars) %>% 
  parameters()
```


<!-- ## ANOVAs -->

<!-- Indices of effect size for ANOVAs, such as partial and non-partial versions of `eta_squared()`, `epsilon_sqared()` or `omega_squared()`, were moved to the [**effectsize**-package](https://easystats.github.io/effectsize/). However, **parameters** uses these function to compute such indices for parameters summaries. -->

<!-- ### Simple -->

<!-- ```{r, warning=FALSE, message=FALSE} -->
<!-- aov(Sepal.Length ~ Species, data = iris) %>%  -->
<!--   parameters(omega_squared = "partial", eta_squared = "partial", epsilon_squared = "partial") -->
<!-- ``` -->

<!-- ### Repeated measures -->

<!-- `parameters()` (resp. its alias `model_parameters()`) also works on repeated measures ANOVAs, whether computed from `aov()` or from a mixed model. -->

<!-- ```{r, warning=FALSE, message=FALSE} -->
<!-- aov(mpg ~ am + Error(gear), data = mtcars) %>%  -->
<!--   parameters() -->
<!-- ``` -->


## Regressions (GLMs, Mixed Models, GAMs, ...)

`parameters()` (resp. its alias `model_parameters()`) was mainly built with regression models in mind. It works for many types of models and packages, including mixed models and Bayesian models.

### GLMs

```{r, warning=FALSE, message=FALSE}
glm(vs ~ poly(mpg, 2) + cyl, data = mtcars) %>% 
  parameters()
```

### Mixed Models

```{r, warning=FALSE, message=FALSE}
library(lme4)

lmer(Sepal.Width ~ Petal.Length + (1|Species), data = iris) %>% 
  parameters()
```

### Bayesian Models

`model_parameters()` works fine with Bayesian models from the **rstanarm** package...

```{r, warning=FALSE, message=FALSE, eval = FALSE}
library(rstanarm)

stan_glm(mpg ~ wt * cyl, data = mtcars) %>% 
  parameters()
```
```{r, warning=FALSE, message=FALSE, echo = FALSE}
library(rstanarm)

stan_glm(mpg ~ wt * cyl, data = mtcars, iter = 500, chains = 2, refresh = 0) %>% 
  parameters()
```

... as well as for (more complex) models from the **brms** package. For more complex models, other model components can be printed using the arguments `effects` and `component` arguments.

```{r, warning=FALSE, message=FALSE, eval=FALSE}
library(brms)
data(fish)
set.seed(123)
model <- brm(bf(
   count ~ persons + child + camper + (1 | persons),
   zi ~ child + camper + (1 | persons)
 ),
 data = fish,
 family = zero_inflated_poisson()
)
parameters(model, component = "conditional")
#> Parameter   | Median |         89% CI |     pd | % in ROPE | ESS |  Rhat
#> ------------------------------------------------------------------------
#> b_Intercept |  -0.87 | [-1.49, -0.08] | 96.80% |     4.80% |  78 | 1.000
#> b_persons   |   0.84 | [ 0.60,  1.06] |   100% |        0% |  75 | 0.997
#> b_child     |  -1.16 | [-1.32, -1.00] |   100% |        0% | 107 | 1.027
#> b_camper1   |   0.74 | [ 0.52,  0.91] |   100% |        0% | 224 | 0.993

parameters(model, effects = "all", component = "all")
#> # Fixed Effects (Count Model) 
#> 
#> Parameter   | Median |         89% CI |     pd | % in ROPE | ESS |  Rhat
#> ------------------------------------------------------------------------
#> (Intercept) |  -0.87 | [-1.49, -0.08] | 96.80% |     4.80% |  78 | 1.000
#> persons     |   0.84 | [ 0.60,  1.06] |   100% |        0% |  75 | 0.997
#> child       |  -1.16 | [-1.32, -1.00] |   100% |        0% | 107 | 1.027
#> camper1     |   0.74 | [ 0.52,  0.91] |   100% |        0% | 224 | 0.993
#> 
#> # Fixed Effects (Zero-Inflated Model) 
#> 
#> Parameter   | Median |         89% CI |     pd | % in ROPE | ESS |  Rhat
#> ------------------------------------------------------------------------
#> (Intercept) |  -0.76 | [-1.66,  0.51] | 87.20% |    10.40% |  98 | 0.992
#> child       |   1.87 | [ 1.37,  2.43] |   100% |        0% | 262 | 0.999
#> camper1     |  -0.83 | [-1.44, -0.22] | 99.20% |     0.80% | 168 | 0.997
#> 
#> # Random Effects (Count Model) 
#> 
#> Parameter | Median |        89% CI |     pd | % in ROPE | ESS |  Rhat
#> ---------------------------------------------------------------------
#> persons.1 |  -0.01 | [-0.40, 0.35] | 59.20% |    57.60% |  80 | 1.012
#> persons.2 |   0.03 | [-0.15, 0.33] | 61.60% |    60.80% |  88 | 0.994
#> persons.3 |  -0.02 | [-0.38, 0.11] | 63.20% |    64.80% |  66 | 1.008
#> persons.4 |   0.00 | [-0.51, 0.29] | 51.20% |    62.40% |  76 | 0.992
#> 
#> # Random Effects (Zero-Inflated Model) 
#> 
#> Parameter | Median |         89% CI |     pd | % in ROPE | ESS |  Rhat
#> ----------------------------------------------------------------------
#> persons.1 |   1.38 | [ 0.58,  2.66] | 97.60% |     1.60% | 108 | 0.992
#> persons.2 |   0.27 | [-0.62,  1.40] | 68.80% |    13.60% | 100 | 1.002
#> persons.3 |  -0.11 | [-1.36,  0.86] | 60.80% |    16.80% |  96 | 0.993
#> persons.4 |  -1.19 | [-2.62, -0.31] | 95.20% |     0.80% | 115 | 0.992
```

## Structural Models (PCA, EFA, CFA, SEM...)

The **parameters** package extends the support to structural models.

### Principal Component Analysis (PCA) and Exploratory Factor Analysis (EFA) 

```{r, warning=FALSE, message=FALSE}
library(psych)

psych::pca(mtcars, nfactors = 3) %>% 
  parameters()
```

```{r, warning=FALSE, message=FALSE, eval = FALSE}
library(FactoMineR)

FactoMineR::FAMD(iris, ncp = 3) %>% 
  parameters()
```
```{r, warning=FALSE, message=FALSE, echo = FALSE}
library(FactoMineR)

FactoMineR::FAMD(iris, ncp = 3, graph = FALSE) %>% 
  parameters()
```


### Confirmatory Factor Analysis (CFA) and Structural Equation Models (SEM)

#### Frequentist

```{r, warning=FALSE, message=FALSE}
library(lavaan)

model <- lavaan::cfa(' visual  =~ x1 + x2 + x3
                       textual =~ x4 + x5 + x6
                       speed   =~ x7 + x8 + x9 ', 
                       data = HolzingerSwineford1939)

model_parameters(model)
```

#### Bayesian

`blavaan` to be done.

## Meta-Analysis

`parameters()` also works for `rma`-objects from the **metafor** package.

```{r, warning=FALSE, message=FALSE}
library(metafor)

mydat <- data.frame(
  effectsize = c(-0.393, 0.675, 0.282, -1.398),
  standarderror = c(0.317, 0.317, 0.13, 0.36)
)

rma(yi = effectsize, sei = standarderror, method = "REML", data = mydat) %>% 
  model_parameters()
```

## Plotting Model Parameters

There is a `plot()`-method implemented in the [**see**-package](https://easystats.github.io/see/). Several examples are shown [in this vignette](https://easystats.github.io/see/articles/parameters.html).
