====== Extract Map Attributes ======

===== Description =====

Extracts general attributes and basic statistics from a map, returning them as a lookup table keyed by a predefined attribute code. All layers of the map are analyzed together, and the resulting table refers to them jointly.

===== Inputs =====

^ Name  ^ Type  ^ Description  ^
| Map  | [[Map Type]]  | Map whose attributes will be extracted.  |

===== Optional Inputs =====

^ Name  ^ Type  ^ Description  ^ Default Value  ^
| Extract Dynamic Attributes  | [[Boolean Value Type]]  | If true, dynamic attributes (null/non-null cell counts, minimum, maximum, sum) are also extracted.  | Yes  |
| Extract Statistical Attributes  | [[Boolean Value Type]]  | If true, statistical attributes (mean, variance, standard deviation, mode, median, unique count) are also extracted.  | Yes  |

===== Outputs =====

^ Name  ^ Type  ^ Description  ^
| Attributes  | [[Lookup Table Type]]  | Table of extracted attributes, keyed by attribute code.  |
| Layer Attributes  | [[Table Type]]  | Table of per-layer attributes, keyed by layer position in the map.  |

===== Group =====

[[Functor List#Map Algebra | Map Algebra]]

===== Notes =====

Each attribute has a predefined name that can be used to retrieve it by name (rather than by numeric key) with the ''tX["NAME"]'' syntax in [[Calculate Map]], [[Calculate Categorical Map]], [[Calculate Value]], and the lookup table calculators.

If an attribute cannot be determined, its entry is omitted from Attributes rather than being filled with a placeholder. Minimum and maximum values are only determined when the map has at least one non-null cell.

**Basic attributes**

^ Key  ^ Predefined Name  ^ Description  ^
| 1  | "lines"  | number of lines  |
| 2  | "columns"  | number of columns  |
| 3  | "cells"  | lines times columns  |
| 4  | "layers"  | number of layers  |
| 5  | "cellHeight"  | cell height, in meters  |
| 6  | "cellWidth"  | cell width, in meters  |
| 7  | "cellArea"  | cell area, in hectares  |
| 19  | "cellType"  | cell type code, see Cell type codes below  |
| 20  | "nullValue"  | null value  |
| 21  | "registrationCoordinateY"  | registration coordinate Y  |
| 22  | "registrationCoordinateX"  | registration coordinate X  |
| 23  | "registrationCellY"  | registration cell Y  |
| 24  | "registrationCellX"  | registration cell X  |
| 25  | "rotationY"  | rotation Y  |
| 26  | "rotationX"  | rotation X  |
| 27  | "originalCellHeight"  | cell height as specified by the projection  |
| 28  | "originalCellWidth"  | cell width as specified by the projection  |

**Dynamic attributes** (present only when Extract Dynamic Attributes is true), computed across all non-null cells of all layers:

^ Key  ^ Predefined Name  ^ Description  ^
| 8  | "nullCells"  | number of null cells  |
| 9  | "nonNullCells"  | number of non-null cells  |
| 10  | "minCell"  | minimum value (excluding null cells)  |
| 11  | "maxCell"  | maximum value (excluding null cells)  |
| 12  | "cellSum"  | sum of the values (excluding null cells)  |

**Statistical attributes** (present only when Extract Statistical Attributes is true), computed across all non-null cells of all layers:

^ Key  ^ Predefined Name  ^ Description  ^
| 13  | "meanCell"  | average (excluding null cells)  |
| 14  | "cellVar"  | variance (excluding null cells)  |
| 15  | "cellStd"  | standard deviation (excluding null cells)  |
| 16  | "modeCell"  | mode (excluding null cells)  |
| 17  | "medianCell"  | median (excluding null cells)  |
| 18  | "uniqueCells"  | total unique occurrences (excluding null cells)  |

**Cell type codes** used by attribute 19 ("cellType"):

^ Code  ^ Cell Type  ^
| 0  | Unsigned 1 Bit Integer  |
| 1  | Signed 8 Bit Integer  |
| 2  | Unsigned 8 Bit Integer  |
| 3  | Signed 16 Bit Integer  |
| 4  | Unsigned 16 Bit Integer  |
| 5  | Signed 32 Bit Integer  |
| 6  | Unsigned 32 Bit Integer  |
| 7  | IEEE 754 32 Bit Real  |
| 8  | IEEE 754 64 Bit Real  |

Layer Attributes has columns "Layer_Index" (the layer's position) and "Layer_Name" (the layer's name); currently the layer name is the only layer-specific attribute returned.

===== Internal Name =====

ExtractMapAttributes

===== Usage examples =====

See practical examples of this functor in [[lesson_6|Lesson 6: Extracting map attributes and basic statistics]]