====== Index operation ======

Used to sum or multiply values, or finding the maximum or minimum value, of a non-scalar [[Block|Block]]. When the target object is 2-dimensional, you must specify which index list to perform the operation on.

===== Creating an index operation =====

From the [[Projects_window|Projects window]]

  * Expand the Project to which you wish to add the index operation by clicking the + symbol next to it. Right-click on ‘Blocks’, or a [[Sub-system|sub-system]] in ‘Blocks’, and select **Index Operation** from the pop-up menu.

From the [[Matrix_window|Matrix window]]

  * Right click an empty diagonal cell of the matrix and select **Index Operation** from the the pop-up menu.

From the [[Blocks_window|Blocks window]]

  * Place the mouse anywhere over the area of this window and right-click on it. Select **New | Index Operation** from the pop-up menu, //or//
  * In the title bar, select **Index Operation** from the **Type** drop-down list and click on the {{:New24.png|New}} button.

===== Editing an index operation =====

|Note|Most block properties can be edited directly in the [[Blocks_window|Blocks window]].|

The block editor is shown by right-clicking the block in a window and selecting **Edit**. In the [[Blocks_window|Blocks window]], you can also show the block editor by selecting the block and clicking the {{:Edit24.png|Edit}} button, or by double-clicking the right-most “validation” column of the block.

The block editor has three tabs:

==== Properties ====

This page lets you edit basic properties such as name, sub-system and base unit. See [[Editing_properties|editing properties]] for more information.

==== Values ====

The values page let you select the target object and which operation to perform.

**Operation** - Choose the operation to perform. You can compute the **sum**, the **product**, the **minimum** or the **maximum** value of an object.

**Object** - Select the object to perform the operation from this list of all the available non-scalar objects.

**Index List** - When you select a 2-dimensional object, you specify here which index list to perform the operation over.

===== Example =====

The expression //doses// is two dimensional. At a specific time point is has the following values:

^Contaminant^Person^Value^
|Lead       |Man   |4    |
|Arsenic    |Man   |1    |
|Mercury    |Man   |6    |
|Lead       |Woman |3    |
|Arsenic    |Woman |8    |
|Mercury    |Woman |6    |

An index operation which finds the maximum over the //Person// indices would yield:

^Contaminant^Value^
|Lead       |4    |
|Arsenic    |8    |
|Mercury    |6    |

===== See also =====

  * [[Blocks_window|Blocks window]]
  * [[Matrix_window|Matrix window]]
  * [[Graph_window|Graph window]]
  * [[Tutorial_4-Using_index_lists_(Advanced)|Tutorial 4-Using index lists (Advanced)]]