Taking your models to new heights
modelbased
is a package helping with modelbased estimations, to easily compute of marginal means, contrast analysis and model predictions.
Installation
The modelbased package is available on CRAN, while its latest development version is available on Runiverse (from rOpenSci).
Type  Source  Command 

Release  CRAN  install.packages("modelbased") 
Development  Runiverse  install.packages("modelbased", repos = "https://easystats.runiverse.dev") 
Once you have downloaded the package, you can then load it using:
Tip
Instead of
library(datawizard)
, uselibrary(easystats)
. This will make all features of the easystatsecosystem available.To stay updated, use
easystats::install_latest()
.
Documentation
Access the package documentation, and checkout these vignettes:
Features
The package is built around 5 main functions:

estimate_means()
: Estimates the average values at each factor levels 
estimate_contrasts()
: Estimates and tests contrasts between different factor levels 
estimate_slopes()
: Estimates the slopes of numeric predictors at different factor levels or alongside a numeric predictor 
estimate_expectation()
: Predict the response variable using the model
These functions are powered by the visualisation_matrix()
function, a smart tool for guessing the appropriate reference grid.
Create smart grids to represent complex interactions
 Problem: I want to graphically represent the interaction between two continuous variable. On top of that, I would like to express one of them in terms of standardized change (i.e., standard deviation relative to the mean).

Solution: Create a data grid following the desired specifications, and feed it to the model to obtain predictions. Format some of the columns for better readability, and plot using
ggplot
.
Checkout this vignette for a detailed walkthrough on visualisation matrices.
library(ggplot2)
library(see)
library(modelbased)
# 1. Fit model and get visualization matrix
model < lm(Sepal.Length ~ Petal.Length * Petal.Width, data = iris)
# 2. Create a visualisation matrix with expected Zscore values of Petal.Width
vizdata < modelbased::visualisation_matrix(model, by = c("Petal.Length", "Petal.Width = c(1, 0, 1)"))
# 3. Revert from expected SD to actual values
vizdata < unstandardize(vizdata, select = "Petal.Width")
# 4. Add predicted relationship from the model
vizdata < modelbased::estimate_expectation(vizdata)
# 5. Express Petal.Width as zscore ("1 SD", "+2 SD", etc.)
vizdata$Petal.Width < effectsize::format_standardize(vizdata$Petal.Width, reference = iris$Petal.Width)
# 6. Plot
ggplot(iris, aes(x = Petal.Length, y = Sepal.Length)) +
# Add points from original dataset (only shapes 2125 have a fill aesthetic)
geom_point2(aes(fill = Petal.Width), shape = 21, size = 5) +
# Add relationship lines
geom_line(data = vizdata, aes(y = Predicted, color = Petal.Width), linewidth = 1) +
# Improve colors / themes
scale_color_viridis_d(direction = 1) +
scale_fill_viridis_c(guide = "none") +
theme_modern()
Estimate marginal means
 Problem: My model has a factor as a predictor, and the parameters only return the difference between levels and the intercept. I want to see the values at each factor level.
 Solution: Estimate modelbased means (“marginal means”). You can visualize them by plotting their confidence interval and the original data.
Checkout this vignette for a detailed walkthrough on marginal means.
# 1. The model
model < lm(Sepal.Width ~ Species, data = iris)
# 2. Obtain estimated means
means < estimate_means(model)
means
## Estimated Marginal Means
##
## Species  Mean  SE  95% CI
## 
## setosa  3.43  0.05  [3.33, 3.52]
## versicolor  2.77  0.05  [2.68, 2.86]
## virginica  2.97  0.05  [2.88, 3.07]
##
## Marginal means estimated at
# 3. Plot
ggplot(iris, aes(x = Species, y = Sepal.Width)) +
# Add base data
geom_violin(aes(fill = Species), color = "white") +
geom_jitter2(width = 0.05, alpha = 0.5) +
# Add pointrange and line from means
geom_line(data = means, aes(y = Mean, group = 1), linewidth = 1) +
geom_pointrange(
data = means,
aes(y = Mean, ymin = CI_low, ymax = CI_high),
size = 1,
color = "white"
) +
# Improve colors
scale_fill_material() +
theme_modern()
Contrast analysis
 Problem: The parameters of my model only return the difference between some of the factor levels and the intercept. I want to see the differences between each levels, as I would do with posthoc comparison tests in ANOVAs.
 Solution: Estimate modelbased contrasts (“marginal contrasts”). You can visualize them by plotting their confidence interval.
Checkout this vignette for a detailed walkthrough on contrast analysis.
# 1. The model
model < lm(Sepal.Width ~ Species, data = iris)
# 2. Estimate marginal contrasts
contrasts < estimate_contrasts(model)
contrasts
## Marginal Contrasts Analysis
##
## Level1  Level2  Difference  95% CI  SE  t(147)  p
## 
## setosa  versicolor  0.66  [ 0.49, 0.82]  0.07  9.69  < .001
## setosa  virginica  0.45  [ 0.29, 0.62]  0.07  6.68  < .001
## versicolor  virginica  0.20  [0.37, 0.04]  0.07  3.00  0.003
##
## Marginal contrasts estimated at Species
## pvalue adjustment method: Holm (1979)
Check the contrasts at different points of another linear predictor
 Problem: In the case of an interaction between a factor and a continuous variable, you might be interested in computing how the differences between the factor levels (the contrasts) change depending on the other continuous variable.
 Solution: You can estimate the marginal contrasts at different values of a continuous variable (the modulator), and plot these differences (they are significant if their 95% CI doesn’t cover 0).
model < lm(Sepal.Width ~ Species * Petal.Length, data = iris)
estimate_contrasts(model, by = "Petal.Length", length = 3)
## Marginal Contrasts Analysis
##
## Level1  Level2  Petal.Length  Difference  95% CI  SE  t(144)  p
## 
## setosa  versicolor  1.00  1.70  [ 0.87, 2.53]  0.34  4.97  < .001
## setosa  versicolor  3.95  1.74  [ 0.16, 3.32]  0.65  2.67  0.023
## setosa  versicolor  6.90  1.78  [1.71, 5.26]  1.44  1.24  0.304
## setosa  virginica  1.00  1.34  [ 0.38, 2.30]  0.40  3.38  0.002
## setosa  virginica  3.95  1.79  [ 0.19, 3.40]  0.66  2.70  0.023
## setosa  virginica  6.90  2.25  [1.19, 5.69]  1.42  1.58  0.304
## versicolor  virginica  1.00  0.36  [1.55, 0.83]  0.49  0.73  0.468
## versicolor  virginica  3.95  0.06  [0.30, 0.42]  0.15  0.37  0.710
## versicolor  virginica  6.90  0.47  [0.22, 1.16]  0.28  1.65  0.304
##
## Marginal contrasts estimated at Species
## pvalue adjustment method: Holm (1979)
# Recompute contrasts with a higher precision (for a smoother plot)
contrasts < estimate_contrasts(model, by = "Petal.Length", length = 20)
# Add Contrast column by concatenating
contrasts$Contrast < paste(contrasts$Level1, "", contrasts$Level2)
# Plot
ggplot(contrasts, aes(x = Petal.Length, y = Difference, )) +
# Add line and CI band
geom_line(aes(color = Contrast)) +
geom_ribbon(aes(ymin = CI_low, ymax = CI_high, fill = Contrast), alpha = 0.2) +
# Add line at 0, indicating no difference
geom_hline(yintercept = 0, linetype = "dashed") +
# Colors
theme_modern()
Generate predictions from your model to compare it with original data
 Problem: You fitted different models, and you want to intuitively visualize how they compare in terms of fit quality and prediction accuracy, so that you don’t only rely on abstract indices of performance.
 Solution: You can predict the response variable from different models and plot them against the original true response. The closest the points are on the identity line (the diagonal), the closest they are from a perfect fit.
Checkout this vignette for a detailed walkthrough on predictions.
# Fit model 1 and predict the response variable
model1 < lm(Petal.Length ~ Sepal.Length, data = iris)
pred1 < estimate_expectation(model1)
pred1$Petal.Length < iris$Petal.Length # Add true response
# Print first 5 lines of output
head(pred1, n = 5)
## Modelbased Expectation
##
## Sepal.Length  Predicted  SE  95% CI  Residuals  Petal.Length
## 
## 5.10  2.38  0.10  [2.19, 2.57]  0.98  1.40
## 4.90  2.00  0.11  [1.79, 2.22]  0.60  1.40
## 4.70  1.63  0.12  [1.39, 1.87]  0.33  1.30
## 4.60  1.45  0.13  [1.19, 1.70]  0.05  1.50
## 5.00  2.19  0.10  [1.99, 2.39]  0.79  1.40
##
## Variable predicted: Petal.Length
# Same for model 2
model2 < lm(Petal.Length ~ Sepal.Length * Species, data = iris)
pred2 < estimate_expectation(model2)
pred2$Petal.Length < iris$Petal.Length
# Initialize plot for model 1
ggplot(data = pred1, aes(x = Petal.Length, y = Predicted)) +
# with identity line (diagonal) representing perfect predictions
geom_abline(linetype = "dashed") +
# Add the actual predicted points of the models
geom_point(aes(color = "Model 1")) +
geom_point(data = pred2, aes(color = "Model 2")) +
# Aesthetics changes
labs(y = "Petal.Length (predicted)", color = NULL) +
scale_color_manual(values = c("Model 1" = "blue", "Model 2" = "red")) +
theme_modern()
Extract and format grouplevel random effects
 Problem: You have a mixed model and you would like to easily access the random part, i.e., the grouplevel effects (e.g., the individuals scores).

Solution: You can apply
estimate_grouplevel
on a mixed model.
See this vignette for more information.
library(lme4)
model < lmer(mpg ~ drat + (1 + drat  cyl), data = mtcars)
random < estimate_grouplevel(model)
random
## Group  Level  Parameter  Coefficient  SE  95% CI
## 
## cyl  4  (Intercept)  3.45  0.56  [4.55, 2.36]
## cyl  4  drat  2.24  0.36  [ 1.53, 2.95]
## cyl  6  (Intercept)  0.13  0.84  [1.52, 1.78]
## cyl  6  drat  0.09  0.54  [1.15, 0.98]
## cyl  8  (Intercept)  3.32  0.73  [ 1.89, 4.74]
## cyl  8  drat  2.15  0.47  [3.07, 1.23]
plot(random)
Estimate derivative of nonlinear relationships (e.g., in GAMs)
 Problem: You model a nonlinear relationship using polynomials, splines or GAMs. You want to know which parts of the curve are significant positive or negative trends.

Solution: You can estimate the derivative of smooth using
estimate_slopes
.
The two plots below represent the modeled (nonlinear) effect estimated by the model, i.e., the relationship between the outcome and the predictor, as well as the “trend” (or slope) of that relationship at any given point. You can see that whenever the slope is negative, the effect is below 0, and vice versa, with some regions of the effect being significant (i.e., positive or negative with enough confidence) while the others denote regions where the relationship is rather flat.
Checkout this vignette for a detailed walkthrough on marginal effects.
# Fit a nonlinear General Additive Model (GAM)
model < mgcv::gam(Sepal.Width ~ s(Petal.Length), data = iris)
# 1. Compute derivatives
deriv < estimate_slopes(model,
trend = "Petal.Length",
by = "Petal.Length",
length = 100
)
# 2. Visualize predictions and derivative
see::plots(
plot(estimate_relation(model)),
plot(deriv),
n_rows = 2
)
Describe the smooth term by its linear parts
 Problem: You model a nonlinear relationship using polynomials, splines or GAMs. You want to describe it in terms of linear parts: where does it decrease, how much, where does it increase, etc.

Solution: You can apply
describe_nonlinear
on a predicted relationship that will return the different parts of increase and decrease.
See this vignette for more information.
model < lm(Sepal.Width ~ poly(Petal.Length, 2), data = iris)
# 1. Visualize
vizdata < estimate_relation(model, length = 30)
ggplot(vizdata, aes(x = Petal.Length, y = Predicted)) +
geom_ribbon(aes(ymin = CI_low, ymax = CI_high), alpha = 0.3) +
geom_line() +
# Add original data points
geom_point(data = iris, aes(x = Petal.Length, y = Sepal.Width)) +
# Aesthetics
theme_modern()
# 2. Describe smooth line
describe_nonlinear(vizdata, x = "Petal.Length")
## Start  End  Length  Change  Slope  R2
## 
## 1.00  4.05  0.50  0.84  0.28  0.05
## 4.05  6.90  0.47  0.66  0.23  0.05
Plot all posterior draws for Bayesian models predictions
See this vignette for a walkthrough on how to do that.
Understand interactions between two continuous variables
Also referred to as JohnsonNeyman intervals, this plot shows how the effect (the “slope”) of one variable varies depending on another variable. It is useful in the case of complex interactions between continuous variables.
For instance, the plot below shows that the effect of hp
(the yaxis) is significantly negative only when wt
is low (< ~4
).
model < lm(mpg ~ hp * wt, data = mtcars)
slopes < estimate_slopes(model, trend = "hp", by = "wt")
plot(slopes)
Visualize predictions with random effects
Aside from plotting the coefficient of each random effect (as done here), we can also visualize the predictions of the model for each of these levels, which can be useful to diagnostic or see how they contribute to the fixed effects. We will do that by making predictions with estimate_relation
and setting include_random
to TRUE
.
Let’s model the reaction time with the number of days of sleep deprivation as fixed effect and the participants as random intercept.
library(lme4)
model < lmer(Reaction ~ Days + (1  Subject), data = sleepstudy)
preds < estimate_relation(model, include_random = TRUE)
plot(preds, ribbon = list(alpha = 0)) # Make CI ribbon transparent for clarity
As we can see, each participant has a different “intercept” (starting point on the yaxis), but all their slopes are the same: this is because the only slope is the “general” one estimated across all participants by the fixed effect. Let’s address that and allow the slope to vary for each participant too.
model < lmer(Reaction ~ Days + (1 + Days  Subject), data = sleepstudy)
preds < estimate_relation(model, include_random = TRUE)
plot(preds, ribbon = list(alpha = 0.1))
As we can see, the effect is now different for all participants. Let’s plot, on top of that, the “fixed” effect estimated across all these individual effects.
fixed_pred < estimate_relation(model) # This time, include_random is FALSE (default)
plot(preds, ribbon = list(alpha = 0)) + # Previous plot
geom_ribbon(data = fixed_pred, aes(x = Days, ymin = CI_low, ymax = CI_high), alpha = 0.4) +
geom_line(data = fixed_pred, aes(x = Days, y = Predicted), linewidth = 2)
Code of Conduct
Please note that the modelbased project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.