About warning

Hi

I send the following mail last night.? Please help us.

-------- Forwarded Message --------
Subject: 	About warning
Date: 	Sun, 16 May 2021 19:10:21 +0900
From: 	Atsuko Nakagawa <nakagawa at hum.nagoya-cu.ac.jp>
To: 	r-sig-mixed-models at r-project.org


Hi

Thank you very much for your help.

When we ran Package lme4 to our longitudinal data, we got following 
warnings repeatedly.

fixed-effect model matrix is rank deficient so dropping 2 columns / 
coefficients
boundary (singular) fit: see ?isSingular 

Nevertheless, we got some results. Are these valid?
When I look for the Q&A in some Statistic Forums, sometimes I found the 
previous answer that we do not have to care these warnings.

In actuality, how do we deal with these warnings?

Thank you for your time.

Atsuko Nakagawa

Graduate School of Humanities and Social Sciences, Nagoya City 
University, JAPAN