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{{ transformations:RuleAction.png}}
====== RULE ======
Category: Transform / Basic\\

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=====Description=====
This action calculates a new column or replaces an existing column, by using one or several ordered IF...THEN...ELSE conditions. The conditions are checked one by one until a satisfying condition is found. When found, the result is calculated and all other conditions are ignored. When no satisfying condition is found, the default calculation is applied.\\

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=====Action settings=====
====Column options====
^Setting^Description^
|Create new column|This option creates a new column with the results of the rule.  Enter a name for the new column in the text box at the right.|
|Replace existing|With this option, select the column that will contain the results of the rule, overwriting the existing values.|
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====Calculated as settings====
^Setting^Description^
|if|An expression that evaluates to either //TRUE// or //FALSE// which determines whether the //then// statement will be processed (i.e., the //then// will run when the //if// expression is TRUE.|
|then|The value inserted into the column when the //if// condition is TRUE.  This can be entered as an expression or static value.  Options:  //this is an expression// or //this is a text or number//.|
You can add more if/then conditions using the //Add more rules// option.  An //else// will be inserted between if/then pairs, indicating that later conditions are only run if previous conditions evaluate to FALSE.  The if/then rules are evaluated in the order entered until one evaluates to TRUE, and the rest are ignored.\\
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====No conditions met options====
^Setting^Description^
|Make empty|If none of the //if// statements evaluate to TRUE, enter an "empty" value.|
|Default to|Options:  //it's an expression// or //it's a text or number//.  Enter either an expression to be evaluated or a static value,\\ in cases where none of the //if// statements evaluate to TRUE.|
|Keep original value|If none of the //if// statements evaluate to TRUE, retain the original value.|

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=====Remarks=====
The order of conditions is significant as conditions are checked starting with the first (top). Therefore, conditions that come first have priority over conditions that come later.

While the same result can be achieved using an expression with nested [[syntax:functions:if]] functions, the use of Rule action is recommended for clarity, readability, and the ease of rearranging the order.

This action doesn't evaluate expressions that shouldn't be evaluated because the condition is or is not true.  For example, it can be used with the //columnexists()// function to perform calculations with columns that are not guaranteed to exist.
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=====Examples=====

====Example #1====
>Add a column that flags countries' Disposable income as "LOW" if 30,000 or below.

===Before (source table)===
^ Country  ^ Gross   ^ Disposable  ^
| United States  |  56067|  45582|
| Australia  |  51050|  32617|
| Switzerland  |  53716|  48414|
| Canada  |  45896|  27469|
 
===After (result table)===
^Country  ^Gross  ^Disposable  ^Low flag  ^
| United States  |  56067|  45582|  |
| Australia  |  51050|  32617|  |
| Switzerland  |  53716|  48414|  |
| Canada  |  45896|  27469|**LOW**  |

===Action parameters:===
>Create new column: Low flag
>__Calculated as:__
>if ([Disposable] <= 30000), then LOW
>If none of the conditions above is met: Default to ""

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=====Community examples=====
  * [[https://community.easymorph.com/t//1530/2|Import figures in “scientific format”]] ([[https://community.easymorph.com/uploads/short-url/poEu3Fy9uLb9DdlWKAPN4VoS8XU.morph|Project]]; Module: //Main//; Group: //Tab 1//; Table: //Table 1//; Action position: //2//)
  * [[https://community.easymorph.com/t//1551/2|How to look up and replace a string of text]] ([[https://community.easymorph.com/uploads/short-url/dvCtD7gg0AHUtXZ7tmQmuHflSYU.morph|Project]]; Module: //Main//; Group: //Tab 1//; Table: //Table 3//; Action position: //5//)
  * [[https://community.easymorph.com/t//1686/2|Aggregation of consecutive date ranges]] ([[https://community.easymorph.com/uploads/short-url/xyC5nPd52hGrMiRXjp5w1RVUTYL.morph|Project]]; Module: //Main//; Group: //Tab 1//; Table: //Easymorph Patient Example Data.xlsx//;\\ Action position: //6//)
  * [[https://community.easymorph.com/t//1697/2|Partial or fuzzy lookup]] ([[https://community.easymorph.com/uploads/short-url/nfnr4o7wX53X2SEaJU5NJ5AzAGt.morph|Project]]; Module: //Main//; Group: //Tab 1//; Table: //Lookup//; Action position: //4//)
  * [[https://community.easymorph.com/t//1876/2|How to report validation failures?]] ([[https://community.easymorph.com/uploads/short-url/x8xqV8QqQbnnI467dxWdhLbXnFr.morph|Project]]; Module: //Main//; Group: //Tab 1//; Table: //Validate data//; Action position: //2//)

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=====Shortcuts=====
Fast ways to create the action:\\
  *Right-click on a column heading, and select "Modify", then "With rule..." from the submenu.
  *Click the drop-down arrow in a column heading and select "Modify", then "With rule..." from the submenu.

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=====See also=====
  * [[transformations:addcolumn|Calculate new column(s)]]
  * [[transformations:replacecolumns|Modify columns(s)]]
  * [[https://community.easymorph.com/t/place-stronger-conditions-first-in-the-rule-action/1113|Community: Place stronger conditions first in the Rule action]]