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  "path": "/t/power-calculations-in-longitudinal-mixed-effects-from-two-measurements-to-three-measurements/28699#post_3",
  "publishedAt": "2026-04-09T19:06:41.000Z",
  "site": "https://discourse.datamethods.org",
  "tags": [
    "lme4.r-universe.dev",
    "Covariance Structures",
    "@Frank"
  ],
  "textContent": "@Frank,\n\nAn FYI, while the older lme() function in the nlme package by Doug et al supported AR1 correlation structures with a continuous response, that had been lacking until just last month in lme4, which was a long standing and frustrating issue. The default in lme4, I believe, has been an unstructured correlation matrix.\n\nNow with version 2.x for lme4, just released early last month, Ben et al have added new features to make it easier to specify alternative correlation structures, which brings those features inline with glmmTMB, which has been an alternative for many of those applications that required these, and other features.\n\nThe combinations of these ME model options and the emmeans package by Russ Lenth, have offered a great deal of flexibility in modeling longitudinal data and generating relevant contrasts.\n\nMore info from Ben here on the recent lme4 updates:\n\nlme4.r-universe.dev\n\n### Covariance Structures\n\nRegards,\n\nMarc",
  "title": "Power Calculations in Longitudinal Mixed Effects - from two measurements to three measurements"
}