mlstats

The mlstats package provides tools for multilevel descriptive statistics and data preparation. It computes within-group and between-group correlations (via variance decomposition or two-level structural equation modeling), intraclass correlation coefficients (ICCs), and descriptive statistics for nested data (e.g., repeated measurements per person), supporting both frequentist (via lme4 or lavaan) and Bayesian (via brms) estimation. Results are formatted according to APA standards and can be exported as tables using gt or tinytable. The package also includes functions for decomposing variables into within-group and between-group components for use in Random Effects Within-Between (REWB) models.

Installation

You can install mlstats from CRAN:

install.packages("mlstats")

You can also install the development version from GitHub:

# install.packages("pak")
pak::pak("felixdidi/mlstats")

Overview

mlstats is built around two main tasks:

• Multilevel descriptives: mldesc() computes means, standard deviations, ranges, ICCs, and a combined within-/between-group correlation matrix in a single call. within_between_correlations() computes only the correlation matrix. Both support multiple print methods for publication-ready output.
• Variable decomposition: decompose_within_between() splits time-varying predictors into within-group deviations (situational fluctuations) and between-group means (stable differences), ready for use in REWB models.

Example

This example uses the simulated media_diary dataset included with mlstats. It mimics a study in which 100 participants completed brief daily surveys for 14 consecutive days (N = 100 persons, T = 1,400 daily observations).

library(mlstats)
data("media_diary")

media_diary |>
  mldesc(
    group = "person",
    vars = c("self_control", "wellbeing", "screen_time", "stress")
  )

## # Multilevel Descriptive Statistics
##   ============ ===== ====== ===== ===== ===== ===== ===== ===== =====
##   variable     n_obs      m    sd range   `1`   `2`   `3`   `4`   icc
##   ------------ ----- ------ ----- ----- ----- ----- ----- ----- -----
## 1 Self control 1,400   4.03  0.83   2–6     –    NA    NA    NA  1.00
## 2 Wellbeing    1,400   4.45  0.87   2–7  .61*     –  .42* -.43*   .46
## 3 Screen time  1,400 128.66 42.29 0–272 -.67* -.34*     –  .29*   .45
## 4 Stress       1,400   3.81  0.91   1–7 -.53* -.38*  .38*     –   .33
##   ============ ===== ====== ===== ===== ===== ===== ===== ===== =====
## # ℹ Within-person correlations above, between-person correlations below the
## #   diagonal.
## # ℹ All correlations marked with a star are significant at p < .05.
## # ℹ Correlations estimated via variance decomposition.
## # ℹ Group-weighted multilevel descriptive statistics computed with mlstats.

Learning more

mlstats comes with documentation vignettes to help you get started:

• Learn a best practice workflow in vignette("mlstats").
• Learn how to report multilevel descriptive statistics in vignette("multilevel-descriptives") and how to transform them into publication-ready multilevel descriptive tables in vignette("tables").
• Learn how to use decomposed variables and interpret effects in Random Effects Within-Between (REWB) models in vignette("rewb-models").
• Learn about the different estimation approaches (decomposition, SEM, and Bayesian) for within- and between-group correlations in vignette("correlation-methods").

References

Bell, A., Fairbrother, M., & Jones, K. (2019). Fixed and random effects models: Making an informed choice. Quality & Quantity, 53(2), 1051–1074. https://doi.org/10.1007/s11135-018-0802-x

Enders, C. K., & Tofighi, D. (2007). Centering predictor variables in cross-sectional multilevel models: A new look at an old issue. Psychological Methods, 12(2), 121–138. https://doi.org/10.1037/1082-989X.12.2.121

Pedhazur, E. J. (1997). Multiple regression in behavioral research: Explanation and prediction (3rd ed.). Harcourt Brace.