Max function problem

What have you done so far? Also, ideally you should supply data in your post in an R-readible format.

Have a look at how to create a reproducible example (reprex)

A handy way to supply sample data is to use the dput() function. See ?dput. If you have a very large data set then something like head(dput(myfile), 100) will likely supply enough data for us to work with.