C'est "Avertissement" pas "Erreur".
You may have a problem but you may not have a problem.
I think we need to see your code and some sample data. See
FAQ Asking Questions
A handy way to supply some sample data is the dput() function. In the case of a large dataset something like dput(head(mydata, 100)) should supply the data we need. Just do dput(mydata) where mydata is your data. Copy the output and paste it here between
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