# [Tex/LaTex] Best practice for mean value of function: bar or overline or something else

math-mode

If you have a function f, it is common to denote its mean value by a line over it, like \bar u. Suppose I have a function like $f_T$, then how should I write the mean value?

Like $\bar f_T$, $\overline{f}_T$ or $\overline{f_T}$? Or something else? Please advise me!!!

This seems a matter of preference to me. I personally always prefer to use \overline, as I find the \bar line to be very short (particularly if you have something wider than a single letter, like f_T). Apart from that preference, I'd point out two small differences between including the _T under the line, or not.

• If by the mean of f_T, you mean: the mean of f, and afterwards specifying some T, I would suggest \overline{f}_T
• If f_T is the actual function you are taking a mean of, I would suggest \overline{f_T}

By your description, I would suggest the second.

In general, if you are unsure, you can always make a command

\newcommand*\mean[1]{\overline{#1}}


and use \mean{f_T}, so you can change to \bar if you'd prefer that at a later point.