View source for Template:Xviews/doc

{{Documentation subpage}}
{{template rating|alpha}}
May be used to generate a bar chart showing page views for a given article or page from a [[#Pageviews file|pageviews file]] downloaded from the <span class=plainlinks>[https://pageviews.wmcloud.org/?project=en.wikipedia.org pageviews tool]</span>. Mock-up; see {{slink||Notes}}.

== Usage ==

{{tlc|xviews}}{{br}}
{{tlc|xviews|''pageviews file''}}

== Parameters ==
There are three optional parameters:
* {{para|1}} – the pageviews file.(Default: [[WP:VAR|{{((}}SUBJECTPAGENAME}}]]; place on Talk page to get pageviews for the article.) See {{slink||Instructions}}.
* {{para|2}} – the count of page view bars to display (optional; alias: {{para|days}}; default: {{xviews/gCOUNT}}; max: 150.) Large values may cause failure, see {{slink||Notes}}.
* {{para|stale}} – number of days when a pageviews file becomes stale. Stale files will not generate a chart; a link to the {{slink||Update instructions}} is provided instead. (optional; default: {{Xviews/gSTALE}}). 

Hooks are in place for additional parameters, not yet implemented:
* {{para|log}} – use logarithmic data points; ideal for spiky or highly variable page view data &nbsp; ''(not implemented)''
* {{para|mode}} – flips the chart from horizontal to vertical &nbsp; ''(not implemented)''

== Examples ==

{{cot|bg=darkseagreen|indent=0.8em|align=left|Example 1. page views for World War II}}
{{tlc|xviews|Talk:World War II/pageviews|days{{=}}45}} ⟶ 
{{xviews|Talk:World War II/pageviews|days=45}} <!-- PEIS reached faster on /doc page for some reason-->
{{cob}}

== Instructions ==

<h3>How-to</h3>
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Displaying an experimental pageviews bar chart for a given article involves these steps:
# add {{tlc|Xreadership}} to the Talk page below the rest of the banners; hit Preview, and click [show].
# open tabs for the /pageviews page (edit it if blue), and for the <span class=plainlinks>[https://pageviews.wmcloud.org/?project=en.wikipedia.org pageviews tool]</span> 
# download the pageviews data from the tool (three months's worth recommended) and copy it to the open <code>/pageviews</code> tab (overwriting any former data), but do not save it yet;
# test in [[WP:PREVIEW|Preview mode]] (important!). If there are [[#Troubleshooting|problems]], replace the call with {{tlc|Xreadership|days{{=}}45}} and preview again. Publish when the bar chart *and* the rest of the page are displayed properly.
# Optional: to view as much pageviews data as possible without blowing up the rest of the page, fine tune the value of {{para|days}} to keep template usage high, but within bounds; i.e. [[WP:PEIS|PEIS]] below 2Mb; 1.7 is better. Be aware that if someone later adds complex templates in a discussion, they may not work if insufficient resources are left after the chart; keep the page on your watchlist and monitor changes.

<h3>Pageviews file</h3><!--no ==wiki header== here-->
This template requires a pageviews file in [[Comma-separated value|CSV format]], which by default is expected to be available as a subpage of the article Talk page where the template is placed. [[WP:POSITIONAL|Positional]] param 1 is available as an override, to point somewhere else. The pageviews file may be placed by bot, or manually by an editor. 

Contents of the pageviews file may be downloaded manually from the <span class=plainlinks>[https://pageviews.wmcloud.org/?project=en.wikipedia.org pageviews tool]</span>. Request output in [[Comma separated variable|CSV]] format, and copy it to a Talk subpage whose [[Wikipedia:Page name#sub|subpagename]] is <code>pageviews</code>; e.g., [[Talk:Cleopatra/pageviews]]. A good amount of data to request is three months' worth. Any amount of data may be copied to the subpage, but the template will only display at most the last 150 lines in the file to avoid issues caused by [[#technical limitations|technical limitations]] with templates.The template has to read the whole pageviews file even if less data is displayed, and long files may exceed some [[#technical limitations|technical limitations]] and cause the template to fail; reducing the pageviews file size may permit more of it to be displayed, than when the total filesize is larger. Empirically, the optimal amount appears to be 60 or 75 days, for Talk pages with an average number of other templates on them. Some pages will show 90 days, or even more. However much data is downloaded to the file, you may always display less than the full amount using param {{para|days}} in order to avoid exceeding [[Help:Template limits|template limits]].

<h3>Maintenance</h3><!--no ==wiki header== here-->
If the pageviews file is not updated, it will eventually reach the staleness threshold (currently, {{Xviews/gSTALE}} days) and after that will not be displayed. To display it again, repeat download step 1 [[#How-to|above]]. You may download and save the pageviews file for a given page as often as you like; just save it on top of the old one. <includeonly><!--The following applies only to Xreadership, not to Xviews:-->To make it easier to know when maintenance is necessary, the summary view of the collapsed Talk page chart banner displays the age of the file in days: the day you download it, it will show "age=1", meaning you have pageview data through yesterday. This value will grow if the pageviews file is not updated, until it hits {{Xviews/gSTALE}}, and then the template will show a prompt message instead of the bar chart.</includeonly>

== Notes ==

This template is a mockup of a replacement for the non-working {{tl|annual readership}} based on {{tl|Graph:Chart}} which was withdrawn for security reasons. It is a proof of concept and if approved, is designed to be replaced by a Lua module. 

<h3>Technical limitations</h3>
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There are various limitations in the template which will disappear in a Lua version, such as reaching the [[WP:PEIS|PEIS]] limit if too many statistics are charted at once. The default value of param {{para|days}} is a throttle to help avoid this. If there are a lot of other templates on the page, you may need do reduce the value of that parameter to stay within limits. See [[Help:Template limits]].

<h3>Troubleshooting</h3><!--no ==wiki header== here-->
* Chart does not display – some cases are recognized by the template and trapped with an error message; others are not.
** recognized errors:
*# missing file – if the pageviews file is missing, you should see a red error message.
*# stale data – if the data in the pageviews file is older than the 'stale' age, then a message about stale data should be emitted. 
** unrecognized:
*# template limits exceeded – if there is no chart and no error message, you may have exceeded one of the [[Help:Template limits|template limits]]. In this case, you may see just the template name instead of any output; this is a sign that PEIS has been exceeded. Try running it in [[WP:Preview|preview mode]]; if PEIS is exceeded, you may see the message, Warning: {{xt|Post-expand include size is too large. Some templates will not be included.}} in a pink box at the top, and the [[WP:parser profiling data|parser profiling data]] will show the PEIS maxed out at "2,097,152 of 2,097,152 bytes". If you see that, try reducing the value of {{para|days}} until it shows output in preview mode, then save it. Reducing the pagefile size will also help; the template reads and processes all the data (multiple times, which a module won't), and if your pagefile has a year's worth of data, you may only be able to display 30 days of it, whereas if you reduce it to three months of data, you can probably display all of it.

<h3>Known issues</h3><!--no ==wiki header== here-->
* Wrapping – in some cases, the page views in the right margin wraps to the next line; this usually only happens with the longest bar in the chart, and especially when the values are greater than 1,000 (and thus require 4 or more characters) 
* length of longest bar – by design, the bar representing the page view statistic with the highest value should be close to the right margin (allowing space for date on the left and view statistic on the right); all other bars are positioned as a fraction of the longest one. Currently, the longest bar will display close to the right margin if all data in the pageviews file is displayed, but if less than all data is displayed (due to use of {{para|days}} or default value) and the largest value in the pageviews file happens to belong to a non-displayed statistic (i.e., one more than three months ago, in the default chart), then it's possible that the displayed bars will appear shorter, as they are still displayed relative to the largest page view statistic in the file, even if it is not displayed. The fix is to display the longest *displayed* statistic close to the right margin, and other bars proportional to it. In practice, this means an adjustment to {{tl|xviews/max views}} to return the value of the largest displayed statistic, not the largest one in the pageviews file.
* x-axis caption – missing the namespace.
* Others: see [[Template talk:Xviews|Talk]].

== Performance ==
This is a mockup intended to be replaced in the medium term by a Lua module, and ultimately by repair to the Graphs problem, so performance of the template isn't really a major issue. Check [[WP:Parser profiling data]] for performance data. One chart with three months of data ({{as written<!--use no template here-->|92}} bars) took 2.32 seconds (real) and 1.86 of 2.09Mb [[WP:PEIS|PEIS]]. Templates don't have local storage, and one upshot is that the template does a great deal of repetitive accesses (> 100) to the pageviews file that would turn into one access in Lua, so performance improvement in a module should be dramatic.

== See also ==
* {{tl|Xreadership}} – template to place a message box with [[Template:Xviews/summary|summary info]] and a collapsed Xviews bar chart onto a Talk page
* {{phab|T334940}} – all Graphs broken on Wikimedia wikis (due to security issue T336556) 
* [[Wikipedia:Village pump (technical)/Archive 205#Graph extension disabled per immediate effect|WP:VPT Graph extension disabled]]
* [https://pageviews.wmcloud.org/?project=en.wikipedia.org Pageviews tool on wmcloud]
* [[WP:Template limits]] – in particular, [[WP:Post-expand include size]]
<includeonly>{{Sandbox other||
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[[Category:Wikipedia formatting templates]]
[[Category:Wikipedia pageviews]]
[[Category:Chart, diagram and graph formatting and function templates]]
}}</includeonly>