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Template:Val

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This template is used to easily present values in scientific notation, including uncertainty and/or units, as prescribed by Wikipedia's Manual of Style. It wraps the entire result in a {{nowrap}} block, so that it never gets broken into separate pieces at the end of a line. (See WP:NBSP for more information on the usage of non-breaking spaces.)

Arguments

There are four ways this template can be used:

  • {{val|number}} - for displaying values without uncertainty/significance.
  • {{val|number|uncertainty}} - for displaying values with uncertainty, like so: 1234±56.
  • {{val|number|upper uncertainty|lower uncertainty}} - for displaying values with uncertainty, like so: 1234+56
    78
    .
  • {{val|number|(significance)}} - for displaying values with significance, like so: 1234(56).

They all take roughly the same arguments

1 The value (must be a valid number)
2 The (upper limit of) uncertainty (must be a valid number) or significance (must be a valid number in parenthesis)
3 The lower limit of uncertainty (must be a valid negative number)
e The exponent for the power of 10 (optional). This will show up in the result as: ×10e
.
sortval Alternative sorting factor to 1
u / ul Activate units and any markup / with a link to a page about the unit (optional / optional)
up / upl Construct units, and this is the "per" unit that is the denominator / with a link to a page about the denominator
Units for the number, specified by u and ul (and up and upl), are replaced by a more aesthetically pleasing HTML representation and can get a link (ul and upl only) if they are in the list found in {{val/unitswithlink}} or if they are supported by {{convert}}). You can specify units using just u; a good example is "ul=m/s", which gets translated to "m·s−1", or you can use u and up, as in "u/up"; a good example is "ul=m|up=s", which gets translated to "m/s".
us / ups Alternative unit code for sorting.
p A prefix for the value (such as ∆, ⌀, etc.; optional).
s A suffix for the value (such as %, optional).
Prefixes (specified by p) and suffixes (specified by s) are put in front of or behind the value as is: this includes spaces. They are inside the nowrap block and will always be on the same line as the value. The parameters that previously provided this functionality (h for header and f for footer) are deprecated and will be ignored.
end Appends something after the main value. For example, {{val|123.24|end=...}} gives 123.24...
errend Appends something after the uncertainty. For example, {{val|123.23|end=...|2.34|errend=...}} gives 123.23...±2.34...
+errend & -errend Appends something after the positive/negative uncertainties. For example, {{val|123.23|end=...|+2.34|+errend=...|-1.23|-errend=...}} gives 123.23...+2.34...
1.23...
fmt Allows alternative formatting using commas to the left of the decimal point as opposed gaps either side. For example, {{val|123123.123123|fmt=commas}} gives 123,123.123123
nocategory If set to any value, errors in the use of this template will not cause the page to be added to the Pages with incorrect formatting templates use category. This is useful for documentation and test pages that do not need to be fixed.
long scale Use |long scale=on to link and sort |u=billion etc. according to the "long scale".

See {{val/testcases}} for a list of examples of the correct output of {{val}} and the errors it may return when incorrectly used.

Errors

There is strict checking on the validity of arguments; any incorrect use will result in an error, which is displayed using {{FormattingError}}. Pages that contain incorrect use of this template will show up on Category:Pages with incorrect formatting templates use.

Format of numbers

{{Val}} produces formatting compliant with Wikipedia's Manual of Style.

The MOS recommends that numbers either be delimited using thin spaces either side of the decimal, or commas to the left and no delimiters to the right. Articles should be consistent wrt the style of delimiting. The template defaults to the former style, this can be adjusted using |fmt= (see above).

Sorting

A hidden sort key is added to the output for sorting in sortable tables. The sort key is based on the main value (parameter |1=) and, if used, the exponent for the power of 10 (parameter |e=) and/or units (parameters |u=, |ul=, |up= and/or |upl=). Where necessary, units are converted to base SI units for the purpose of the sort key, which is produced by {{ntsh}}. Several units are covered; see § How to add units for those which are not. To omit the sort key use |sortable=off.

Examples

{{val|1234567890}}  →  1234567890
{{val|1.23456789}}  →  1.23456789
{{val|1.2345678}}  →  1.2345678
{{val|21563.252564425}}  →  21563.252564425 [1]
Uncertainty/significance
{{val|1.234|0.005}}  →  1.234±0.005
{{val|1.234|+0.005|-0.006}}  →  1.234+0.005
0.006
{{val|1.234|(5)}}  →  1.234(5)
Units
{{val|1.234|u=m}}  →  1.234 m
{{val|1.234|u=m2}}  →  1.234 m2
{{val|1.234|ul=m}}  →  1.234 m
{{val|123.4|ul=USgal}}  →  123.4 US gal
{{val|12.34|ul=mpgimp}}  →  12.34 mpg-imp
{{val|12.34|u=deg}}  →  12.34°
{{val|1.234|0.005|u='}}  →  1.234±0.005
{{val|1.234|+0.005|-0.006|u="}}  →  1.234+0.005
0.006
Exponents
{{val|1.234|e=5|ul=m}}  →  1.234×105 m
{{val|1.234|0.056|e=7}}  →  (1.234±0.056)×107
{{val|1.23456|+0.00007|-0.00008|e=-9|ul=m/s}}  →  1.23456+0.00007
0.00008
×109 m/s
{{val|1.234|0.056|e=7|ul=psi}}  →  (1.234±0.056)×107 psi
{{val|1.234|(5)|e=-2}}  →  1.234(5)×102
Prefix/suffix
{{val|p=Δ |12.34}}  →  Δ 12.34
{{val|p=+|12.34|u=%}}  →  +12.34%
{{val|12.34|0.25|s=%}}  →  12.34±0.25%
Numerator/Denominator
{{val|1.234|e=7|ul=W|up=m2}}  →  1.234×107 W/m2
More examples
See the testcases at {{val/testcases}}.

Performance impact

For most uses, in the text of articles, Template:Val will not restrict performance, but when used inside the wikitext markup of large templates, there are some restrictions. When displaying integer amounts, Template:Val has an internal expansion depth of 15 levels, but for numbers with decimal portions, it uses 22 levels, or more.

How to add units

  1. Add the unit to Template:Val/unitswithlink. All of Val's units have the option for a link to there article and so are are represented there.
  2. Add the unit to Template:Val/unitswithlink/test. All of Val's units must look the same whether they are linked or not, per the Manual of Style for dates and numbers, and this test proves that. The unit you will add is required to have a link version and a non-link version for stylistic reasons (including the ability of editors to avoid overlinking). The link version will be added to Template:Val/unitswithlink to process the ul and upl parameters.
  3. Depending on the previous step, the non-link version might need to be added to Template:Val/units to process the u and up parameter; it depends on whether or not the unit needs markup, or if the characters users will give to the ul or u parameter are different than what is displayed. (There may be other, technical, reasons why Template:Val/units could need an entry.)

Note these points before adding units:

  • For composite units you should probably link the whole, not individual units. For example the line you add would say |m·s-1=[[Velocity|m·s{{sup|−1}}]] linking to Velocity, not |m*s-1=[[Metre|m]]·[[Second|s]]{{sup|−1}}. List of common physics notations has many examples of composite units that have their own page.
  • The val user can compose their own divisor unit from an existing unit, for example writing {{val|99|ul=m|upl=s}} to render their own "99 m/s" with two links: m to Meter and s to Second.
  • The val user can compose their own multiplier units by using the end parameter to prepend a string. For example, in a geology article, to prepend "Ma", to the unit in 333 14C yr BP they could write {{val|333|end= Ma|ul=uBP}}, rendering "333 Ma 14C yr BP". (The end parameters cannot be linked.)

After adding a unit, if it has an SI prefix, units which are not #Sorting correctly inside of tables may have to be added to {{Val/sortkey/unit}}. That template, like other subtemplates of Val, is a switch function whose list of cases are the list of units, and whose result for each unit is a number related to the units multiplier, such as 1000 for km.

FAQ and comments

  • Q: Why should I use Val?
A1: Val formats numbers:
A2: Val preserves spacing:
  • It makes sure the value does not wrap at the end of a line, so that it can always be read as a single value on one line in the text.
  • It spaces the various parts of the value where they should be
A3: Val automates the markup for, and a link to a displayed unit.
A4: Val helps make Wikipedia more consistent. It adheres to the Wikipedia Manual of Style for numbers. Updates to the MoS can be applied to this template, and result in automatic modification on values that use it. All this makes sure all values on all pages have the same look and feel because they will all use the same spacing, font size, positioning, etc, and makes updating and checking by the bots easier because they can recognize a value for what it is.
  • Q: Why not use <math>?
A: For the same reasons HTML might be preferred over TeX:
  • Because the font in math tags differs both in face and size from the prose, which can disturb the layout of a page when used inline with the prose.
  • You cannot cut and paste a bitmap image rendered by the Latex.
  • Images are slower to load and use more bandwidth, which is especially bad for the mobile version of Wikipedia.
  • <math> does not automatically easily align to the Manual of Style for numbers.
  • Q: Are there any known issues with Val?
A1: Because numbers can only be stored with a limited precision by Wikipedia servers, val cannot handle very large numbers, such as 123456789123456789. This is reported using a {{FormattingError}}, so it should be easy to spot. Because there is very limited use for such large numbers, there is no fix planned for this.
A2: This template has been in full use on many pages for quite some time without major problems or breaking changes. Technically, there is no good reason not to try Val.
  • Q: How should I use Val?
A1: Val probably already has your unit on its current list. If not, then your unit can be added.
A2: To avoid over linking switch from the ul= to the u= parameter of the given unit.

See also