Calculate Map
Description
Computes a new continuous raster map by evaluating an algebraic or logical expression independently for every cell of the output map. The expression result is always computed as a real (floating-point) value and then converted to the output map's chosen Cell Type. Use this functor when the expression produces continuous or measured values; use Calculate Categorical Map instead when the expression produces integer class codes that downstream functors should treat as categories.
This is one of Dinamica EGO's five calculator functors. Its abbreviated (shorthand) syntax is #. See Calculator functor shorthand in the EGO Script documentation for the verbose and abbreviated forms, and Calculate Functors — Complete Operator Documentation for the full expression language reference.
Inputs
| Name | Type | Description |
|---|---|---|
| Expression | Image Expression Type | Algebraic or logical formula used to compute each output cell. Must be enclosed in square brackets [ ] in EGO Script. |
Optional Inputs
| Name | Type | Description | Default Value |
|---|---|---|---|
| Cell Type | Cell Type Type | Data type for each output cell. | Signed 32 Bit Integer |
| Null Value | Null Value Type | Sentinel value representing “no data” in the output. | .default |
| Result Is Sparse | Boolean Value Type | If true, only non-null cells are stored, saving memory at the expense of random-access speed. This is an advanced port. | No |
| Result Format | Map Type | Reference map whose spatial format (extent, resolution, projection) is applied to the output; its category information, if any, is ignored. Prefer this port over a Number Map hook when a map is needed only for format purposes, since a hook defines an identifier in the expression namespace and blocks abbreviated syntax if that identifier goes unused in the expression. This is an advanced port. | .none |
Outputs
| Name | Type | Description |
|---|---|---|
| Result | Map Type | Computed output map. Its dimensions come from the connected input maps, or from Result Format when given. |
Group
Notes
Connecting data inputs
All maps, tables, and scalar values referenced in the expression must be connected to the functor's ports before writing the expression, using hook functors:
- Maps → Number Map → referenced in the expression as i1, i2, …, i100
- Tables and lookup tables → Number Table → referenced as t1, t2, …, t100
- Scalar values → Number Value → referenced as v1, v2, …, v100
In the abbreviated syntax, operands are referenced directly by the variable name they are bound to, prefixed with # for maps, % for tables, and $ for values — eliminating the hook block entirely.
Spatial context and image virtualization
The expression is evaluated independently once per cell across the output map. Two spatial keywords are available inside the expression:
- line — the row index of the current cell, starting at 1
- column — the column index of the current cell, starting at 1
When the expression references more than one map, all of them are evaluated at the same current cell — i1 and i2 always refer to the same spatial location. Connected maps do not need matching extent, resolution, or pixel dimensions: Dinamica EGO reconciles this automatically through image virtualization, transparently wrapping each input in a virtual version sharing a common extent and the highest resolution among the inputs. The one requirement that virtualization does not relax is projection — all connected maps must share the same projection.
The iX[LINE, COL] form samples a map at an explicit coordinate rather than the current cell. Coordinates outside the image boundary are mirrored back into range. For a row coordinate cellLine in an image of N rows, cellLine is normally expected to be in the range [1, N]. When cellLine is outside this range, it is mirrored back: if cellLine ≤ 0, the effective row is 1 − cellLine (for instance, cellLine = 0 → row 1, cellLine = −1 → row 2, cellLine = −2 → row 3); if cellLine > N, the effective row is 2N + 1 − cellLine (for instance, cellLine = N+1 → row N, cellLine = N+2 → row N−1, cellLine = N+3 → row N−2). The same formula applies independently to the column coordinate cellCol. If the target cell is null, the result is 0 rather than null.
Available expression features
All expression language features are available — there are no restrictions. For the full operator reference, see The Expression Language in the Calculate Functors documentation, or the Image Expression Type page for the GUI editor and a navigable operator index.
Null value handling
Null propagation, the two map-calculator exceptions (iX[LINE, COL] returning 0 and neighbourhood functions excluding nulls), and defensive patterns are covered in Null Value Handling in the Calculate Functors documentation. If the computed result exceeds the range of the chosen Cell Type, that cell is also written as null rather than wrapping or clipping.
Performance
Expression calculations can be compiled to native code automatically (requires the optional native expression support package), delivering near-C performance without any change to the model.
Internal Name
CalculateMap
Usage examples
- CalculateMap practical examples in the Calculate Functors documentation