Calculate Lookup Table Values

Description

Generates a new lookup table by evaluating an expression once per row of a base lookup table. The keys of the output table are inherited from the base table; the values are computed by the expression.

This functor is one of five in the calculator family. Use it when you need to recompute the values of an existing lookup table row by row, keeping the same key structure. If you also need to recompute the keys, use Calculate Lookup Table Keys And Values instead.

The abbreviated syntax (also called shorthand) for this functor is %. See Calculator functor shorthand in the EGO Script documentation for the full syntax of both the verbose and abbreviated forms, and Calculate Functors — Complete Operator Documentation for the complete expression language reference.

Inputs

Name	Type	Description
Value Column Expression	Image Expression Type	The formula evaluated for each row. The result becomes the value for that row's key in the output table, written using the image expression editor. Must be enclosed in square brackets [ ] in EGO Script.

Optional Inputs

Name	Type	Default	Description
Key Column Name	Name Type	None	Name of the key column in the output lookup table. If omitted, the corresponding name from the base table is used.
Value Column Name	Name Type	None	Name of the value column in the output lookup table. If omitted, the corresponding name from the base table is used.
Base Lookup Table	Lookup Table Type	None	The lookup table whose key set drives iteration. When not provided, the lowest-indexed connected Number Table (verbose form) or the first lookup table referenced by name in the expression (abbreviated form) is used — not a union of all connected tables.

Output

Name	Type	Description
Result	Lookup Table Type	A lookup table with keys from the base table and values computed by the expression.

Group

Table

Notes

Connecting data inputs

Tables, lookup tables, and scalar values referenced in the expression must be connected to the functor's ports before writing the expression, using hook functors:

Tables and lookup tables → Number Table → referenced in the expression as t1, t2, …, t100

Scalar values → Number Value → referenced as v1, v2, …, v100

Maps cannot be connected — there is no cell context in this functor. In the abbreviated syntax, tables are referenced as %variableName and values as $variableName.

Row iteration context

The expression is evaluated once per row of the base lookup table. Two keywords reflect the current row inside the expression:

line — the key of the current row

column — the value already associated with that key in the base lookup table

This allows the expression to read the row's existing value directly via column, and to look up related values from other connected tables using the current row's key — for example, t1[line] retrieves the value from table t1 whose key matches the current row.

Available expression features

Image operators (iX), neighbourhood functions, neighbourhood indexing, and convolution are not available — there is no spatial grid. Available features are arithmetic and logical operators, scalar references (vX), table and lookup table queries (tX[...]) in all single-key and multi-column forms, and the line and column row-context keywords. See The Expression Language for the complete reference, or Image Expression Type for the navigable operator index.

Null value handling

Null propagation rules and defensive patterns are covered in Null Value Handling in the Calculate Functors documentation.

Internal Name

CalculateLookupTableValues