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calculate_categorical_map [2012/03/14 21:26] hermann [Optional Inputs] |
calculate_categorical_map [2022/08/19 23:48] (current) admin [Notes] |
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| ^ Name ^ Type ^ Description ^ | ^ Name ^ Type ^ Description ^ | ||
| - | | Expression | [[Image Expression Type|Image Expression]] | Algebraic or logical expression used to calculate the output map. | | + | | Expression | [[Image Expression Type]] | Algebraic or logical expression used to calculate the output map. | |
| ===== Optional Inputs ===== | ===== Optional Inputs ===== | ||
| ^ Name ^ Type ^ Description ^ Default Value ^ | ^ Name ^ Type ^ Description ^ Default Value ^ | ||
| - | | Cell Type | [[Cell Type Type|Cell Type]] | Data cell type | Signed 32 Bit Integer | | + | | Cell Type | [[Cell Type Type]] | Data cell type | Signed 32 Bit Integer | |
| - | | Null Value | [[Null Value Type|Null Value]] | Null value | Default((Based on the value of the Cell Type input.)) | | + | | Null Value | [[Null Value Type]] | Null value | Default((Based on the value of the Cell Type input.)) | |
| - | | Result Is Sparse | [[Bool Type| Bool]] | If true, the resulting map is created as a sparse image. Sparse images have the advantage of storing only the cells containing non-null values, but they have diminished access time. | False | | + | | Result Is Sparse | [[Boolean Value Type]] | If true, the resulting map is created as a sparse image. Sparse images have the advantage of storing only the cells containing non-null values, but they have diminished access time. | False | |
| + | | Result Format | [[Map Type]] | Map representing the output format. Any category information presents in the given map is not used as part of the map format. | None | | ||
| ===== Outputs ===== | ===== Outputs ===== | ||
| ^ Name ^ Type ^ Description ^ | ^ Name ^ Type ^ Description ^ | ||
| - | | Result | [[Categorical Map Type|Categorical Map]] | Output map of classes or categories | | + | | Result | [[Categorical Map Type]] | Output map of classes or categories | |
| ===== Group ===== | ===== Group ===== | ||
| Line 30: | Line 31: | ||
| The expression result is calculated as a real value and converted to the data cell type of the output map. | The expression result is calculated as a real value and converted to the data cell type of the output map. | ||
| - | If the calculation of the expression diverges or if the data cell type is not large enough, the corresponding cell is filled with the null value. | + | If the calculation of the expression diverges, the corresponding cell is filled with the null value. In practice, it means that every time a null value is found in a expression calculation, the calculation results in null value, unless the occurrence of the null value is isolated from the rest of the expression by a special operator like ''[[image_expression_type#image_operators_and_functions|isNull()]]'' or ''[[image_expression_type#general_operators|?]]''. |
| + | |||
| + | The examples below illustrates: | ||
| + | |||
| + | ^ Example ^ Analysis ^ | ||
| + | | <code cpp>i1 / 0</code> | The expression always results in null value (division by zero). | | ||
| + | | <code cpp>i1 + i2 / i3 ^ 3</code> | If the current cell of any of the images involved in the calculation is null value, the expression results in null value . | | ||
| + | | <code cpp>if isNull(i1) then | ||
| + | 1 | ||
| + | else | ||
| + | 2 | ||
| + | </code> | The expression never results in null value. | | ||
| + | | <code cpp>if isNull(i1) then | ||
| + | i2 | ||
| + | else | ||
| + | i3 | ||
| + | </code> | The expression might result in null value depending on the the value of i2 and i3. | | ||
| + | | <code cpp>(100 / i2) ? 0</code> | The expression never results in null value. | | ||
| + | | <code cpp>(100 / i2) ? i1</code> | The expression might result in null value depending on the the value of i1. | | ||
| + | |||
| + | If the data cell type is not large enough, the corresponding cell is also filled with the null value. | ||
| + | |||
| + | The category information for the resulting map is automatically derived from its cell values. | ||
| The list of mathematical and logical operators that can be employed in the logic/algebraic expression can be found in the [[Image Expression Type | image expression reference]]. | The list of mathematical and logical operators that can be employed in the logic/algebraic expression can be found in the [[Image Expression Type | image expression reference]]. | ||
| The maps used by the "Calculate Categorical Map" must be provided by a corresponding [[Number Map]], the tables must be provided by a corresponding [[Number Table]] and the values must be provided by a corresponding [[Number Value]]. | The maps used by the "Calculate Categorical Map" must be provided by a corresponding [[Number Map]], the tables must be provided by a corresponding [[Number Table]] and the values must be provided by a corresponding [[Number Value]]. | ||
| + | |||
| + | For additional information about how the null values are handled during image and value calculation, see [[Image Expression Null Value Handling|this reference]]. | ||
| ===== Internal Name ===== | ===== Internal Name ===== | ||
| CalculateCategoricalMap | CalculateCategoricalMap | ||