Adding tilde or bar

[#1]

I have a plot wich shows the mean and the median.

For the legend I want the mean to be shown in the legend as an X with a bar and the median as an X with a tilde as they do it in math.

I discoverd that for Greek letters the chr(...) can be used

http://www.fileformat.info/info/charset/UTF-32/list.htm

My best try to far for the tilde:

= Mean & X& chr(126)

But this doesn't give me the desired result.

So how can i make the tilde appear on top of the X ?