Thanks both of you,

I suspect that you two are using very different rules to define "readable characters", and for Aaron to get a close correlation and Fabian not to get any correlation implies to me that Fabian is stripping out the things that are not linked to article size, and that Aaron may be leaving such things in.

For reasons that I'm going to pretend I don't understand, we have some articles with a lot of redundant spaces. Others with so few you'd be correct in thinking that certain editors have been making semiautomated edits to strip out those spaces. I suspect that Fabian's formulae ignores redundant spaces, and that Aaron's does not.

I picked on alt text because it is very patchy across the pedia, but usually consistent at article level. I.e if someone has written a whole paragraph of alt text for one picture they have probably done so for every picture in an article, and conversely many articles will have no alt text at all.

Similarly we have headings, and counterintuitively it is the subheadings that add most non display characters. So an article like Peasant's revolt will have 32 equals signs for its 8 headings, but 60 equal signs for its 10 subheadings. 92 bytes which I suspect one or both of you will have stripped out. The actual display text of course omits all 92 of those bytes, but repeats the content of those headings and subheadings in the contents section.

The size of sections varies enormously  from one article to another, and if there are three or fewer sections the contents section is not generated at all. I suspect that the average length of section headings also has quite a bit of variance as it is a stylistic choice. So I would expect that a "display bytes" count that simply stripped out the multiple equal signs would still be a pretty good correlation with article size, but a display bytes count that factored in the complication that headings and subheadings are displayed twice as they are repeated in the contents field, would have another factor drifting it away from a good correlation with raw byte count.

But probably the biggest variance will be over infoboxes, tables, picture  captions, hidden comments and the like. If you strip all of them out, including perhaps even the headings, captions and table contents, then you are going to get a very poor fit between article length and readable byte size. But I would be surprised if you could get Fabian's minimum display size of 95 bytes from 6,000 byte articles without having at least one article that consisted almost entirely of tables and which had been reduced to a sentence or two of narrative. So my suspicion is that Aaron's plot is at least including the displayed contents of tables et al whilst Fabian is only measuring the prose sections and completely stripping out anything in a table.

Both approaches of course have their merits, and there are even some editors who were recent edit warring to keep articles they cared about free from clutter by infoboxes and tables.

Regards

Jonathan

On 5 August 2013 21:16, Floeck, Fabian (AIFB) <fabian.floeck@kit.edu> wrote:
Hi,

thanks for your feedback Jonathan and Aaron.

@Jonathan: You are rightfully pointing at some things that could have been done differently, as this was just an ad-hoc experiment.  What I did was getting the curl result of "http://en.wikipedia.org/w/api.php?action=parse&prop=text&pageid=X"  and running it through BeautifulSoup [1] in Python.
Regarding references: yes, all the markup was stripped away which you cannot see in form of readable characters as a human when you look at an article. Take as an example [2]: in the final output (which was the base for counting chars) what is left in characters of this reference is the readable "[1]" and " ^ William Goldenberg at the Internet Movie Database".
Regarding alt text: it was completely stripped out. This can arguably be done different, if you see it as "readable main article text" as well.
You are sure right that including these would lead to a higher correlation. Looking at samples from the output, the increase in correlation will however not be very big, but that's a mere hunch. Anyway, this was not what I was looking for. I wanted to compare really only the readable text you see directly when scrolling through the article.
What is another issue is the inclusion of expandable template listings as I mentioned in my first mail. Are the long listings of related articles "main, readable article text"?  I suppose not, but we did not filter them out yet.


@Aaron, I'm pretty sure I didn't make a mistake, but before I can answer your mail: What exactly does this content_length API call give you back (I'm not aware of that). Takes the Wikisyntax and strips it of tags and comments? Or the HTML shown in the front-end including all content generated by templates minus all mark-up? Only in the ladder case would this be comparable in any way to what I have done. Please clarify and send me the concrete API call. I don't think your content_length is the length of the readable front-end text as I used it.
(On a side note: I'm unsure why you paste the complete results of a linear regression, as a Pearson correlation will perfectly suffice in such a simple bivariate case. They - due to the nature of these statistical methods - of course yield the same results in this case. Or was there any important extra information that I missed in these regression results?).

Best,

Fabian


[1] http://www.crummy.com/software/BeautifulSoup/bs4/doc/
[2] http://en.wikipedia.org/wiki/William_Goldenberg#cite_note-1


On 05.08.2013, at 01:15, Aaron Halfaker <aaron.halfaker@gmail.com> wrote:

> (note that I posted this yesterday, but the message bounced due to the attached scatter plot.  I just uploaded the plot to commons and re-sent)
>
> I just replicated this analysis.  I think you might have made some mistakes.
>
> I took a random sample of non-redirect articles from English Wikipedia and compared the byte_length (from database) to the content_length (from API, tags and comments stripped).c
>
> I get a pearson correlation coef of 0,9514766.
>
> See the scatter plot including a linear regression line.  See also the regress output below.
>
> Call:
> lm(formula = byte_len ~ content_length, data = pages)
>
> Residuals:
>    Min     1Q Median     3Q    Max
> -38263   -419     82    592  37605
>
> Coefficients:
>                 Estimate Std. Error t value Pr(>|t|)
> (Intercept)    -97.40412   72.46523  -1.344    0.179
> content_length   1.14991    0.00832 138.210   <2e-16 ***
> ---
> Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1
>
> Residual standard error: 2722 on 1998 degrees of freedom
> Multiple R-squared: 0.9053,   Adjusted R-squared: 0.9053
> F-statistic: 1.91e+04 on 1 and 1998 DF,  p-value: < 2.2e-16
>
>
> On Mon, Aug 5, 2013 at 12:59 AM, WereSpielChequers <werespielchequers@gmail.com> wrote:
> Hi Fabian,
>
> That's interesting. When you say you stripped out the html did you also strip out the other parts of the references? Some citation styles will take up more bytes than others, and citation style is supposed to be consistent at the article level.
>
> It would also make a difference whether you included or excluded alt text from readable material as I suspect it is non granular - ie if someone is going to create alt text for one picture in an article they will do so for all pictures.
>
> More significantly there is a big difference in standards of referencing , broadly the higher the assessed quality and or the more contentious the article the more references there will be.
>
> I would expect that if you factored that in there would be some correlation between readable length and bytes within assessed classes of quality, and the outliers would include some of the controversial articles like Jerusalem (353 references)
>
> Hope that helps.
>
> Jonathan
>
>
> On 2 August 2013 18:24, Floeck, Fabian (AIFB) <fabian.floeck@kit.edu> wrote:
> Hi,
> to whoever is interested in this (and I hope I didn't just repeat someone else's experiments on this):
>
> I wanted to know if a "long" or "short" article in terms of how much readable material (excluding pictures) is presented to the reader in the front-end is correlated to the byte size of the Wikisyntax which can be obtained from the DB or API; as people often define the "length" of an article by its length in bytes.
>
> TL;DR: Turns out size in bytes is a really, really bad indicator for the actual, readable content of a Wikipedia article, even worse than I thought.
>
> We "curl"ed the front-end HTML of all articles of the English Wikipedia (ns=0, no disambiguation, no redirects) between 5800 and 6000 bytes (as around 5900 bytes is the total en.wiki average for these articles). = 41981 articles.
> Results for size in characters (w/ whitespaces) after cleaning the HTML out:
> Min= 95 Max= 49441 Mean=4794.41 Std. Deviation=1712.748
>
> Especially the gap between Min and Max was interesting. But templates make it possible.
> (See e.g. "Veer Teja Vidhya Mandir School", "Martin Callanan" -- Allthough for the ladder you could argue that expandable template listings are not really main "reading" content..)
>
> Effectively, correlation for readable character size with byte size = 0.04 (i.e. none) in the sample.
>
> If someone already did this or a similar analysis, I'd appreciate pointers.
>
> Best,
>
> Fabian
>
>
>
>
> --
> Karlsruhe Institute of Technology (KIT)
> Institute of Applied Informatics and Formal Description Methods
>
> Dipl.-Medwiss. Fabian Flöck
> Research Associate
>
> Building 11.40, Room 222
> KIT-Campus South
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>
> Phone: +49 721 608 4 6584
> Fax: +49 721 608 4 6580
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> E-Mail: fabian.floeck@kit.edu
> WWW: http://www.aifb.kit.edu/web/Fabian_Flöck
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--
Karlsruhe Institute of Technology (KIT)
Institute of Applied Informatics and Formal Description Methods

Dipl.-Medwiss. Fabian Flöck
Research Associate

Building 11.40, Room 222
KIT-Campus South
D-76128 Karlsruhe

Phone: +49 721 608 4 6584
Fax: +49 721 608 4 6580
Skype: f.floeck_work
E-Mail: fabian.floeck@kit.edu
WWW: http://www.aifb.kit.edu/web/Fabian_Flöck

KIT – University of the State of Baden-Wuerttemberg and
National Research Center of the Helmholtz Association


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