====Calc====

Performs a calculation on either a //frame// or the table items inside the frame.

===Parameters===

^Name^Default^Meaning^
|name||The name of the final attribute/column|
|value||The value to be written. [[substitution|Substitutable]].|
|where||A condition that must be met for the calculation to happen.|
|else||The value to set if the //where// condition is not true. If blank, no value is set.|
|target||//frame// to force the calculation to run on frame values instead of table columns|

===Description===

This function performs a calculation on a frame, or - if the frame contains a table - the individual items within the table.

This will normally be applied to every column/frame, unless a //where// condition is specified. If a 'where' condition exists, the calculation will only happen on frames and columns that match the condition.

===Example===

If the frame contains the following attributes...

^Attribute^Value^
|Width|100|
|Height|100|

<code javascript>
{
   "type": "calc",
   "name": "Area",
   "value": "{Width} * {Height}"
}
</code>

The final results will include the //Area// attribute with a value of 10,000. If 'Width' and 'Height' were in the table instead, a new **column** called 'Area' would be added.

===Target===

Calculations can happen in two places - in the //rows of the table// or in the //data in the frame//. 

By default, the calculation will run on rows of the **table** if the frame contains a table. You can force it to perform a calc on the frame data by setting the **target** parameter to 'frame'.

===Where, Else & Empty Values===

Note that if you are using the //where// condition, values aren't written to the frame/table rows unless...

1) The condition is //true//,
2) The condition is //false// and column is empty (a blank value is added to the column),
3) The condition is //false// and **else** has been set, in which case the 'else' value is written. 

This means that the **calc** function will create //empty// values, but not replace //existing// values.