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Dear all stat users
Earlier this month I sent the message below to allstat. I received a variety of replies confirming that there is not a stand alone good html coding for creating the character for the sample mean which I wished. A big thank you to all who kindly replied.
Most of the suggestions pointed me to extension to html which could not be supported for universal use with my electronic system or were suggestive of a little overkill for one character. I did try the suggestion made under reply 6 but the outcome looked a little out of place in the middle of the rest of my text.
In the end I used a simple draw facility to create the 'x-bar' symbol and was able to embed it in my text by capturing the image and pointing to it via a URL. This was very easy to do and I was surprised to discover that the resultant character looked very pretty, much better than would have been possible had I used the Equation Editor in MS Word to create my image.
Necessity is the mother of invention!
Previous request of 13 October
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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.
Best wishes
Margaret
Reply 1
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!
Reply 2
Hi Margaret,
I think you might be unlucky with this one.
Here is an excellent webpage which covers some
html special characters:
http://www.xs4all.nl/~dimaroan/htl/characters.html#symbols
but if you want to generate some for yourself then open my
attachment and click the button. You will find 'mean a' at
number 257 and 'mean c' at 275, etc but only a few letters
are catered for.
I image one could devise a method using DHTML and the
div structure but then it would all get a bit too complicated.
Reply 3
HTML doesn't fit for this :(
The graphics approach (for the whole equation usually) is the best I've
used
to get round it, but it's a poor solution.
I should look to see if an of the Unicode fonts carry these symbols,
but I
haven't yet and not yet worked out how to address them in html
Reply 4
The official list of characters available in html is at:
http://www.w3.org/TR/html4/sgml/entities.html#h-24.3
It seems that overline exists only as an independent character.
A natural solution is unicode which has combining diacriticals:
http://www.unicode.org/charts/PDF/U0300.pdf
Therefore, this should work:
<meta CONTENT="text/html CHARSET=UTF-8">
xÝ <!-- should be x overline -->
but I find it is not supported on my browser.
Never use MS Word equation editor. It produces very poor quality
typesetting.
If you want to use an image, tex2im produces far better results and is
much easier to use:
http://www.nought.de/tex2im.php
Reply 5
I faced the same problem a few years ago when I first began putting together the on-line stats text
http://faculty.vassar.edu/lowry/webtext.html
After trying every HTML device I could figure out for X-bar, I finally gave up and simply used Latin letter M -- which for students is probably a better mnemonic for Mean than X-bar anyway. For Greek-letter notations I resorted to usinng small images of the ones I chiefly needed: lower-case mu, lower- and upper-case sigma, and lower-case chi. There are other ways of doing Greek-letter notations, though they tended to give different results on different platform-browser combinations. The real trick was in rendering complex formulaic structures in HTML. I finally figured out it could be done via carefully crafted borderless tables. The result is a bit clunky, though it gets the job done well enough.
Reply 6
Use <span> instead of <div>. To get the bar from being so high, use
a capital X and then reduce the font size.
That would come out to:
>> <style type="text/css">
>> #overline {text-decoration: overline}
>> </style>
>> <span id=overline>x,</span>
Reply 7
Hi,
Probably overkill for that particular query but when I need to write
maths
in html, I use a very useful cgi called mimeTeX:
http://www.forkosh.com/mimetex.html
Once installed, you simply write the LaTeX code as you usually would,
and
the picture is generated on the fly. You can also leave it in the cache
(better if the page receives a lot of hits).
It's fairly easy to install and doesn't require TeX. Just ask your
sysadmin
if you're having difficulties. The page also refers to other solutions.
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