The estimate in linear mixed model SAS code.

Hi guys, how can i get the equivalent of the estimate code used in proc mixed in SAS linear mixed-method models in R.

The estimate statement is used to show the expected change in the dependent variable given a value of the independent variable. This is what it looks like in SAS.

PROC MIXED DATA=exerclong;
CLASS id group(ref='2')/ref=first;
MODEL y = group day group*day/solution;
random intercept/subject=ID;

  • We use the estimate statement to get predictions based on fixed covariate values;
    estimate 'Weight group: day 6 change in strength intercept 0 group 0 0 day 6 group*day 0 6;

My R code is something like this.

model1= lmer(y ~ factor(group) + Day + factor(group):Day + (1 |id), data = exerclong)

I have tried the predict and fit contrast function but looks like they are not appropriate to predict the value of y at a particular day, say day 6.

Can someone help with this?

There isn't a reproducible example provided, so our help maybe limited, but the lmer cheat sheet is always a good start for checking syntax for Mixed Effects models: mixed model - R's lmer cheat sheet - Cross Validated

This is also a good resource as it seems you are using a nested model: https://rpsychologist.com/r-guide-longitudinal-lme-lmer

Outside of that, I would recommend fitting a very basic Mixed effects model first to see if your code works for predicting before introducing additional terms.