Tablehead of dataframe - overline letters

[hcs]

Hello, I want to overline letters in the tablehead (top row) and row names (because I generally expressed averages in this way).
After hours and hours I didn´t find a way.
Can anyone help me?

[jrkrideau]

We lead to know a bit more about of what you are doing.

We need a reproducible example (reprex)

FAQ: What's a reproducible example (`reprex`) and how do I create one?

Why reprex? Getting unstuck is hard. Your first step here is usually to create a reprex, or reproducible example. The goal of a reprex is to package your code, and information about your problem so that others can run it and feel your pain. Then, hopefully, folks can more easily provide a solution. What's in a Reproducible Example? Parts of a reproducible example: background information - Describe what you are trying to do. What have you already done? complete set up - include any library() calls and data to reproduce your issue. data for a reprex: Here's a discussion on setting up data for a reprex make it run - include the minimal code required to reproduce your error on the data…

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.