View source for Template:Calculate increment/doc

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== What it does ==

Calculates suitable increments for {{tl|scalemarkers}}.
Increments are 1, 2 or 5 times an appropriate power of 10.

Variable 1 = from;
Variable 2 = to.

Examples:

{{evd|calculate increment|10|30}}

== Problems it has ==

It doesn't deal with small (<10) scales yet.


== How it does it ==

First we need to select the "base value" - i.e. what we're going to multiply by the power of 10.
We use the following brackets:
:14<35: 20
:35-70 : 50
:70->14: 10

To generate the first two digits is quite laborious. This code generates a suitably rounded number; we need to divide that by 10 ''n'' times.

<code>{{{3|1}}} round (2-{{len|{{#expr:abs ({{{1|0}}} - {{{2|1}}})}}}})}}</code>


{{#expr:

( {{#expr:abs ({{{1|0}}} - {{{2|1}}})}} round (2-{{len|{{#expr:abs ({{{1|0}}} - {{{2|1}}})}}}})) 

/ 

( 1
   {{#if:
      {{#expr: ({{len|{{#expr:abs ({{{1|0}}} - {{{2|1}}})}}}} - 1) >= 0 }}|
      {{loop|{{#expr: ({{len|{{#expr:abs ({{{1|0}}} - {{{2|1}}})}}}} - 1)}}|/10}}|
      {{loop|-{{#expr: ({{len|{{#expr:abs ({{{1|0}}} - {{{2|1}}})}}}} - 1)}}|*10}}
    }}
)
}}

----


Then we need to select the power of 10.

{{#expr: ({{len|{{#expr:abs ({{{1|0.1}}} - {{{2|10}}})}}}} - 1)}}; 
{{#expr:
    {{#if:
      {{#expr: ({{len|{{#expr:abs ({{#expr:abs {{{1|00}}}}} - {{#expr:abs {{{2|1}}}}})}}}} - 1) >= 0 }}|
      10 {{loop|{{#expr: ({{len|{{#expr:abs ({{#expr:abs {{{1|00}}}}} - {{#expr:abs {{{2|1}}}}})}}}} - 2)}}|*10}}|
      10 {{loop|-{{#expr: ({{len|{{#expr:abs ({{#expr:abs {{{1|00}}}}} - {{#expr:abs {{{2|1}}}}})}}}} - 2)}}|/10}}
    }}
}}

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[[Category:Mathematical function templates]]
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