[R] [FORGED] Re: display double dot over character in plotmath?

[Rolf Turner]

On 14/05/17 06:10, David Winsemius wrote:
>
>> On May 13, 2017, at 5:47 AM, Ranjan Maitra <maitra at email.com> wrote:
>>
>> On Fri, 12 May 2017 23:39:14 -0700 Daniel Nordlund <djnordlund at gmail.com> wrote:
>>
>>> On 5/12/17 4:55 PM, Ranjan Maitra wrote:
>>>> Hi,
>>>>
>>>> Is it possible to display double dot (umlaut) over a character such as would be possible using \ddot x in LaTeX? I can do this using tikzDevice but I wanted something simpler to point to.
>>>>
>>>> Here is an example of what I would like to do, but it is not quite there:
>>>>
>>>> require(ggplot2)
>>>> data<-as.data.frame(c("a","b","c","a","b","c"))
>>>> colnames(data)<-"Y"
>>>> data$X<-c(1:6)
>>>> data$Z<-c(1,2,3,1,2,3)
>>>>
>>>> ggplot(data, aes(x=X)) + geom_line(aes(y = Z), size=0.43) + xlab(expression(atop(top,bold(Age~"à"))))
>>>>
>>>> I would like to put in a double dot over the "a" in the x-axis instead of "`".
>>>>
>>>> Many thanks for any suggestions and best wishes,
>>>> Ranjan
>>>>
>>>
>>> You haven't told what OS you are using, but with Windows OS, you can get
>>> the 'ä' by making sure the NUMLOCK key is on, hold down the alt key and
>>> press 0228 on the numeric keypad.
>>>
>>>
>>
>> I am sorry, I use a linux operating system. I use Fedora 25 but the student I wanted to show this uses Ubuntu, though I don't know if the distribution matters.
>
> On a Mac it is cmd-u followed by the vowel of your choice. Perhaps you should do a google search on the topic of getting umlauted characters for the distro of your choice?
>

Well, Linux is not Mac.  For which I am everlastingly thankful.

I believe the following works on both Fedora and Ubuntu:

(1) First add/set a "compose" key:

In my current system (Ubuntu 16.04.2; Mate Desktop 1.12.1) the sequence 
of clicks is:

System -> Control Center -> Keyboard -> Layouts -> Options
        -> Position of Compose key -> [e.g.] Left Win

Clicking on "Left Win" inserts a tick mark in the little white box.  On 
my keyboard the "Left Win" key is to the left of the "Alt" key, which is 
to the left of the space bar.  It displays the (yeuchh!!!) Windoze 
symbol, a distorted window in black and white.  This key is totally 
useless for anything else, so one might as well use it for the compose key.

(2) Then do: <compose key> <letter> <accent>.  E.g

     ' <compose key> a " ' gives  ' ä '.

Note: Do *not* hold the compose key down while pressing the other
keys.  Press the compose key and release it; then press "a" (nothing
appears) then press ' " ' --- and bingo, ä appears.

HTH

cheers,

Rolf Turner

P. S.  Of course you just need to do the "set a compose key" bizzo 
*once* and then it is set and works forever more.  Until you change or 
bugger up your OS. :-)

R. T.

-- 
Technical Editor ANZJS
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276