Summary of Model Parameters

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(), with some notable differences:

Correlations and t-tests

Frequentist

cor.test(iris$Sepal.Length, iris$Sepal.Width) %>% 
  parameters()
#> Parameter1        |       Parameter2 |     r |     t |  df |     p |        95% CI |  Method
#> --------------------------------------------------------------------------------------------
#> iris$Sepal.Length | iris$Sepal.Width | -0.12 | -1.44 | 148 | 0.152 | [-0.27, 0.04] | Pearson
t.test(mpg ~ vs, data = mtcars) %>% 
  parameters()
#> Parameter | Group | Mean_Group1 | Mean_Group2 | Difference |     t |    df |      p |          95% CI |                  Method
#> -------------------------------------------------------------------------------------------------------------------------------
#> mpg       |    vs |       16.62 |       24.56 |       7.94 | -4.67 | 22.72 | < .001 | [-11.46, -4.42] | Welch Two Sample t-test

Bayesian

library(BayesFactor)

BayesFactor::correlationBF(iris$Sepal.Length, iris$Sepal.Width) %>% 
  parameters()
#> Parameter | Median |        89% CI |     pd | % in ROPE |              Prior | Effects |   Component |   BF
#> -----------------------------------------------------------------------------------------------------------
#> rho       |  -0.11 | [-0.23, 0.02] | 92.90% |    43.13% | Cauchy (0 +- 0.33) |   fixed | conditional | 0.51
BayesFactor::ttestBF(formula = mpg ~ vs, data = mtcars) %>% 
  parameters()
#> Parameter  | Median |          89% CI |     pd | % in ROPE |              Prior | Effects |   Component |     BF
#> ----------------------------------------------------------------------------------------------------------------
#> Difference |  -7.30 | [-10.15, -4.58] | 99.98% |        0% | Cauchy (0 +- 0.71) |   fixed | conditional | 529.27

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

glm(vs ~ poly(mpg, 2) + cyl, data = mtcars) %>% 
  parameters()
#> Parameter        | Coefficient |   SE |         95% CI |     t | df |      p
#> ----------------------------------------------------------------------------
#> (Intercept)      |        2.04 | 0.39 | [ 1.27,  2.80] |  5.22 | 28 | < .001
#> mpg [1st degree] |       -0.33 | 0.61 | [-1.53,  0.87] | -0.53 | 28 | 0.599 
#> mpg [2nd degree] |        0.10 | 0.32 | [-0.54,  0.74] |  0.31 | 28 | 0.762 
#> cyl              |       -0.26 | 0.06 | [-0.38, -0.14] | -4.14 | 28 | < .001

Mixed Models

library(lme4)

lmer(Sepal.Width ~ Petal.Length + (1|Species), data = iris) %>% 
  parameters()
#> Parameter    | Coefficient |   SE |       95% CI |    t |  df |      p
#> ----------------------------------------------------------------------
#> (Intercept)  |        2.00 | 0.56 | [0.90, 3.10] | 3.56 | 146 | < .001
#> Petal.Length |        0.28 | 0.06 | [0.17, 0.40] | 4.75 | 146 | < .001

Bayesian Models

model_parameters() works fine with Bayesian models from the rstanarm package…

library(rstanarm)

stan_glm(mpg ~ wt * cyl, data = mtcars) %>% 
  parameters()
#> Parameter   | Median |          89% CI |     pd | % in ROPE |  Rhat | ESS |               Prior
#> -----------------------------------------------------------------------------------------------
#> (Intercept) |  53.16 | [ 42.36, 61.52] |   100% |        0% | 1.002 | 188 | Normal (0 +- 60.27)
#> wt          |  -8.19 | [-11.59, -4.40] |   100% |     0.20% | 1.006 | 184 | Normal (0 +- 15.40)
#> cyl         |  -3.71 | [ -4.88, -1.77] |   100% |     0.20% | 1.000 | 206 |  Normal (0 +- 8.44)
#> wt * cyl    |   0.76 | [  0.19,  1.25] | 98.40% |    32.00% | 1.004 | 179 |  Normal (0 +- 1.36)

… 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.

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)

library(psych)

psych::pca(mtcars, nfactors = 3) %>% 
  parameters()
#> # Rotated loadings from Principal Component Analysis (varimax-rotation)
#> 
#> Variable |   RC2 |   RC3 |   RC1 | Complexity | Uniqueness
#> ----------------------------------------------------------
#> mpg      |  0.66 | -0.41 | -0.54 |       2.63 |       0.10
#> cyl      | -0.62 |  0.67 |  0.34 |       2.49 |       0.05
#> disp     | -0.72 |  0.52 |  0.35 |       2.33 |       0.10
#> hp       | -0.30 |  0.64 |  0.63 |       2.40 |       0.10
#> drat     |  0.85 | -0.26 | -0.05 |       1.19 |       0.21
#> wt       | -0.78 |  0.21 |  0.51 |       1.90 |       0.08
#> qsec     | -0.18 | -0.91 | -0.28 |       1.28 |       0.06
#> vs       |  0.28 | -0.86 | -0.23 |       1.36 |       0.12
#> am       |  0.92 |  0.14 | -0.11 |       1.08 |       0.12
#> gear     |  0.91 | -0.02 |  0.26 |       1.16 |       0.10
#> carb     |  0.11 |  0.44 |  0.85 |       1.53 |       0.07
#> 
#> The 3 principal components (varimax rotation) accounted for 89.87% of the total variance of the original data (RC2 = 41.43%, RC3 = 29.06%, RC1 = 19.39%).
library(FactoMineR)

FactoMineR::FAMD(iris, ncp = 3) %>% 
  parameters()
#> # Loadings from Factor Analysis (no rotation)
#> 
#> Variable     | Dim.1 | Dim.2 | Dim.3 | Complexity
#> -------------------------------------------------
#> Sepal.Length |  0.75 |  0.07 |  0.10 |       1.05
#> Sepal.Width  |  0.23 |  0.51 |  0.23 |       1.86
#> Petal.Length |  0.98 |  0.00 |  0.00 |       1.00
#> Petal.Width  |  0.94 |  0.01 |  0.00 |       1.00
#> Species      |  0.96 |  0.75 |  0.26 |       2.05
#> 
#> The 3 latent factors accounted for 96.73% of the total variance of the original data (Dim.1 = 64.50%, Dim.2 = 22.37%, Dim.3 = 9.86%).

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

Frequentist

library(lavaan)

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

model_parameters(model)
#> # Loading type
#> 
#> Link          | Coefficient |   SE |       95% CI |      p
#> ----------------------------------------------------------
#> visual =~ x1  |        1.00 | 0.00 | [1.00, 1.00] | < .001
#> visual =~ x2  |        0.55 | 0.10 | [0.36, 0.75] | < .001
#> visual =~ x3  |        0.73 | 0.11 | [0.52, 0.94] | < .001
#> textual =~ x4 |        1.00 | 0.00 | [1.00, 1.00] | < .001
#> textual =~ x5 |        1.11 | 0.07 | [0.98, 1.24] | < .001
#> textual =~ x6 |        0.93 | 0.06 | [0.82, 1.03] | < .001
#> speed =~ x7   |        1.00 | 0.00 | [1.00, 1.00] | < .001
#> speed =~ x8   |        1.18 | 0.16 | [0.86, 1.50] | < .001
#> speed =~ x9   |        1.08 | 0.15 | [0.79, 1.38] | < .001
#> 
#> # Correlation type
#> 
#> Link              | Coefficient |   SE |       95% CI |      p
#> --------------------------------------------------------------
#> visual ~~ textual |        0.41 | 0.07 | [0.26, 0.55] | < .001
#> visual ~~ speed   |        0.26 | 0.06 | [0.15, 0.37] | < .001
#> textual ~~ speed  |        0.17 | 0.05 | [0.08, 0.27] | < .001

Bayesian

blavaan to be done.

Meta-Analysis

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

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()
#> Parameter | Coefficient |   SE |         95% CI |     z |      p | Weight
#> -------------------------------------------------------------------------
#> Study 1   |       -0.39 | 0.32 | [-1.01,  0.23] | -1.24 | 0.215  |   9.95
#> Study 2   |        0.68 | 0.32 | [ 0.05,  1.30] |  2.13 | 0.033  |   9.95
#> Study 3   |        0.28 | 0.13 | [ 0.03,  0.54] |  2.17 | 0.030  |  59.17
#> Study 4   |       -1.40 | 0.36 | [-2.10, -0.69] | -3.88 | < .001 |   7.72
#> Overall   |       -0.18 | 0.44 | [-1.05,  0.68] | -0.42 | 0.676  |

Plotting Model Parameters

There is a plot()-method implemented in the see-package. Several examples are shown in this vignette.