MultiTable

New to Analytica 4.6. Present in experimental form in Analytica 4.5.

MultiTable(i1,i2,...)(src1, src2, ...)

A MultiTable provides a unified virtual view of multiple sources of data in a single edit table. The sources can consist of both editable tables and computed non-editable results, both depicted within the cells of a single table. When you change a cell, you are actually changing the original cell in the source, not a copy.

Best practice in Analytica modeling is generally to keep different types of information in different variables; however, you may want to present an end-user with a unified table view, with different columns depicting different items. The MultiTable gives you a way to provide such a view without sacrificing the desired practice of keeping separate data items separate.

For example, suppose Startup_cost and Probability_success are both edit tables, indexed by Project. Then the MultiTable defined as:

MultiTable(Item)(Startup_cost,Probability_success)

displays both in the same edit table, indexed by Item and Project, and the user can edit either item directly from this view.

MultiTable is the inverse of SubTable in that MultiTable unifies multiple sources into one view, whereas SubTable is used to view or reorganize a single source.

Creating a MultiTable

Before you create a MultiTable, you need to create or identify one or more indexes that your data sources will vary over. For example, if you want a different data source to appear in each column of your table, then you'll need a column index, and you'll need to fill in the labels for each column as you define the index.

Next, create a variable to hold your MultiTable and press Ctrl+E to place your cursor in the definition field.

In the Object Finder, select the Array library and scroll down to find and select MultiTable. Then, press the Indexes button.

Select the indexes that your MultiTable data sources will vary along. These are not the indexes of your data sources themselves.

The table initially displays the "Meta expressions" view so that you can specify the data sources for the table. The meta-expression selector controls which view you are in.

Specifying Data Sources

Whenever you need to specify or change which data source should appear in a MultiTable, use the meta-expressions selector to change to meta-expressions view.

Here is an example of meta-expressions.

In the above meta-expressions view, Option_type, Stock_symbol, Strike_price and Expiration_date are identifiers of other edit tables. These will be editable columns. Stock_price_lookup(Stock_Symbol) is a call to a User-Defined Function, and its computed value will appear in this column. The last cell contains Mid(Contract_valuation), so that the computed mid-value of Contract_valuation will be displayed. When you want the computed value of a variable, you must surround its identifier with Mid in this fashion, otherwise its definition will appear in the cell and will be editable.

Editable sources

An editable source reflects the contents of another edit table in your model, a slice of an edit table, or the definition of another variable. When a user edits these cells in the multitable, they are actually changing the data is the specified source definition or table. In meta-expression view, an editable source is specified in one of the following ways.

• X : An identifier. The definition of X, or the edit table (or SubTable or MultiTable of X) is depicted.
• X[I=v] : A Slice or Subscript of another table. That slice is depicted in an editable form.

The source can be a scalar variable, an edit table, a SubTable or another MultiTable. Rather arbitrary transformations that be accomplished by nesting SubTables and MultiTables.

Computed sources

The following are computed expressions, which are evaluated and they resulting value displayed in a non-editable form with a gray background.

• 31.4, "Text": Literal values (numbers, quoted text)
• Mid(X): Displays the computed mid-value of the variable X
• F(...): Any function call other than Slice or Subscript, including calls to User-Defined Functions, are evaluated.
• x+y : An expression, such as one involving arithmetic operations, is evaluated.

Here are a few additional examples:

• Mid(X) : computes and displays the mid-value of X
• Abs(X) : displays the absolute value of the (mid-value) of X
• Mean(X) : computes and displays the mean of X
• 1.2 : displays the number, 1.2, in a non-editable cell
• "Some text" : displays the text, without quotes, in a non-editable cell

A computed expression or computed variable CAN depend on the values of other data sources that appear in the same MultiTable. When you do this, the computed value will change when the user changes the input cells and presses the green check button.

Viewing the Data

After you have specified the data sources in meta-expression view, change the meta-expression selector to Show Cells to see the actual data.

When cells can be editied

In browse mode, data is only editable if it is associated with an input node. This means that if your MultiTable variable has an input node, then all table sources can be changed from browse mode (and thus, from Analytica Player or Cloud Player). Otherwise, if one source has an input node and another does not, then the cells corresponding to the source with the input node can be changed, while those corresponding to the other source cannot be changed from browse mode.

Computed values can never be edited.

Examples

Here is an example of an editable value and computed value in the same table:

Index Base := ["Decimal", "Hex"]
Variable x := 123
Variable HexConverter := MultiTable(Base)(x,NumberToText(x,"Hexadecimal"))

The edit table displays like this:

The first cell can be edited, and when you change it and press the green check, the Hex value is computed and displayed.

Dimensionality

The dimensions of the MultiTable content are the union of the indexes from all sources and of the MultiTable index(es).

A MultiTable works best when your sources all have the same dimensionality. When one source does not have an index present in another source, a single cell in the source will map to multiple cells in the MultiTable; hence, you'll see the same value multiple places, and when you change it, multiple cells will change. The source retains its original dimensionality, so if the value doesn't vary along an index in the source, it won't vary along that index is the MultiTable. You may temporarily see a difference in these cells after you first enter a value, but they will become consistent as soon as you press the Green check.

Number Formats

When number formats are set for the source tables, those formats are used in the corresponding column of the MultiTable.

When a meta-expression is of the form Mid(X), then X's number format is used. For arbitrary expressions, the number format of the MultiTable's own variable is used.

See Also

• SubTable
• Table
• Mid, Mean, Sample -- used for specifying computed results.
• Subscript, Slice, Subscript/Slice Operator