On 13-Oct-05 Margaret MacDougall wrote:
> I would be most grateful for suggestions on how best to code the
> conventional symbol for the sample mean (which I am taking to be a
> small x with a bar immediately above it) in the language of html.
>
> At present, I am using the following approach:
>
> <style type="text/css">
>#overline {text-decoration: overline}
> </style>
> <div id=overline>x,</div>
>
> However, this tends to give a rather make-shift result, as the
> 'overline' tends to sit rather aloof from the x. Moreover, the
> character is forced onto a new line and therefore is not embedded in my
> sentence as wished.
>
> I have consulted several good html books and discovered that whilst
> listings of characters and codes are made for many characters including
> latin letters with circumflexes, the character I am after is not
> represented.
>
> I am learning html almost from scratch and expect that a more
> experienced user could offer some code which has worked for them in the
> past.
>
> An alternative approach would be to capture as an image the result of
> creating my desired character using an MS Word equation editor.
> However, this seems a little far fetched for just one character.
>
> Thank you in advance for your suggestions.
I don't think you can! I'm no expert on HTML either (and if there
are any experts out there we'd love to be put right).
I've looked around a bit. There seems to be a consensus that
you can't do much in the way of mathematical notation in
standard HTML.
The nearest I've found -- which will only work in special
circumstances -- used a "proposed" extension to HTML called
"MATHML".
The syntax given there was
<MATH><ABOVE>x</ABOVE></MATH>
with the caveat "Unfortunately most of the existing browsers do
not recognize the <MATH> tags, so you just get an x. The same
effect can be achieved in non<MATH> enabled browsers using a
<TABLE> construction; i.e.
<TABLE><TH>_<BR>x</TH></TABLE>
which gives [display of x-bar on a separate line]"
See http://www2.sjsu.edu/faculty/watkins/html.htm
On my browsers (mozilla, firefox) the MATH did not work, and
the TABLE method put the x-bar on a new line, with the bar a
little too far above the x (just as described by Margaret).
I suspect, however, that the Opera browser does recognise MATH.
That's still no good, however, for people who don't use it!
The accented characters which are available in HTML at least
include those given as single entities in standard extended
ASCII character sets, such as iso-8859-1 which I'm using now,
and which your mail reader should render correctly, such as
á À å ç ê ï ø ü (only a selection) along with some stand-alone
accents.
These correspond to single ASCII codes and are not composed as
composite characters. Combinations of letter and accent which
are not amongst those available (e.g. above) in the character
set do not exist in HTML.
So, unless it's already a standard single character, you
cannot get it in HTML. In particular (apart from what may be
possible using <MATH>...</MATH>) you can't instruct HTML to
place an arbitrary mark as an "accent" to some other mark.
So, although the requisite stand-alone accent is available
in the iso-8859-1 set at position 175, the "macron" accent
(¯), and you can indeed get it displayed in HTML by entering
¯
in your HTML, you can't as far as I can see instruct HTML
to display an "x" and then put a "¯" above it.
I agree that using Word + Equation Editor to get a bitmap
that you can import is overkill. And I'm personally no
admirer of the Equation Editor anyway. (Haven't we been
here before, and exactly on the "x-bar" topic? I recall that
pre-MedStats exchanges on this between Martin, John and me
about this were what first got us acquainted!)
Despite all this, I have two practical suggestions.
The first, for something as simple as x-bar, is simply to
write "x-bar". This will be readily understood, especially
if you initially explain that "x-bar stands for an x with a
bar over it; unfortunately this cannot be represented in
HTML so I'll just call it 'x-bar'".
The second is where you have occasion to use more than the
occasional mathematical symbol so that you need the reader
to see proper mathematical notation.
For web purposes, the ideal format for this is PDF. The
PDF display software Acrobat Reader is freely available
for most computer platforms from the Adobe website
http://www.adobe.com
So you just put a link to a PDF file in your web page,
and if the person reading it has installed Acrobat Reader
then they can see it exactly as you intended, and also
print it out. Again, the can download and save the PDF
file, so can readily refer to it later. Nowadays I assume
that nearly everyone has Acrobat Reader available so I have
no qualms about sending them PDF files.
The main issue for this suggestion is creating the file
in PDF format in the first place.
You might use Word (with Equation Editor) to create a Word
document which displays the mathematics more or less as
you want it.
<ASIDE>People who want it really right, however, will use
software intended for formatting to precise typesetting
standards, such as TeX/LaTeX and groff which are both free,
and available for Windows and Unixoid systems, and commercial
products such as McKichan's "Scientific Word", which also
claims to be able to export the results directly to HTML
"with mathematics exported as graphics or as MathML."
For LaTeX and groff too there is the possibility to do it
this way, using embedded graphics for equations (e.g. a
program called LaTeX2HTML, which is another free program).
The advantage of using software which incorporates this
approach is that the user, while preparing the document,
simply types in whatever makes it look right on screen.
Then the ecporting to HTML is a single operation, and the
software takes care of embedding the graphics when required.
However, for the real thing the PDF route is the way to go.
There is no limit to the complexity of what can be represented
in PDF, and no limit to the precision with which it can be
represented. (Whether the software you used to create it can
match this, however, is another question).</ASIDE>
Suppose, then, that you have a suitable Word document.
I've heard (though not experienced) that recent versions of
Word can export to PDF (or there's a converter).
However, if not (or not in your case), then you can print
to file using one of the PostScript printer drivers
(e.g. Apple LaserPlus).
Now you have to convert the PostScript file to PDF. Adobe's
commercial Acrobat Distiller will do this (and is the "industry
standard" since both PostScript and PDF are Adobe's creations).
Free options include ghostscript (whose ps2pdf utility
does the job) and somewhat more refined programs which
are specialised for the job such as Frank Siegert's
PStill.
The resulting PDF file will display the mathematics as
well as (but probably no better than) it appeared in your
original Word document.
Hoping this helps -- and is not too discouraging!
Ted.
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Date: 14-Oct-05 Time: 01:11:39
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