fixed-effect model matrix is rank deficient

Machine Learning and Modeling
1

Hi, why get this warning message when run LMM in R?
fixed-effect model matrix is rank deficient so dropping 1 column / coefficient
Thank you!

2

Hi @Comede_way -

What R is trying to tell you is that your dataset has a linear combination of variables. Meaning, some set of columns colA + colB = colC. This can also occur (I believe) if one of your columns is a constant value across all observations. This causes the linear algebra to fail, where the solution is to remove any column that's part of the equation.

Ideally, you'll go back to your data and drop the proper column(s) yourself instead of relying on R "being helpful".

Best,
Randy

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