Field Calculator
- Author: V.Olaya (c) 2004, O.Conrad (c) 2011, J.Spitzmueller, scilands GmbH (c) 2022
- Menu: Table | Calculus;Shapes | Attributes
Description
The table calculator calculates a new attribute from existing attributes based on a mathematical formula. Attributes are addressed by the character 'f' (for 'field') followed by the field number (i.e.: f1, f2, ..., fn) or by the field name in square brackets (e.g.: [Field Name]). Examples: - sin(f1) * f2 + f3 - [Population] / [Area] One can also use the drop-down-menu to append fields numbers to the formula. If the use no-data flag is unchecked and a no-data value appears in a record's input, no calculation is performed for it and the result is set to no-data. Following operators are available for the formula definition:
| + | Addition |
| - | Subtraction |
| * | Multiplication |
| / | Division |
| abs(x) | Absolute Value |
| mod(x, y) | Returns the floating point remainder of x/y |
| int(x) | Returns the integer part of floating point value x |
| sqr(x) | Square |
| sqrt(x) | Square Root |
| exp(x) | Exponential |
| pow(x, y) | Returns x raised to the power of y |
| x ^ y | Returns x raised to the power of y |
| ln(x) | Natural Logarithm |
| log(x) | Base 10 Logarithm |
| pi() | Returns the value of Pi |
| sin(x) | Sine, expects radians |
| cos(x) | Cosine, expects radians |
| tan(x) | Tangent, expects radians |
| asin(x) | Arcsine, returns radians |
| acos(x) | Arccosine, returns radians |
| atan(x) | Arctangent, returns radians |
| atan2(x, y) | Arctangent of x/y, returns radians |
| min(x, y) | Returns the minimum of values x and y |
| max(x, y) | Returns the maximum of values x and y |
| gt(x, y) | Returns true (1), if x is greater than y, else false (0) |
| x > y | Returns true (1), if x is greater than y, else false (0) |
| lt(x, y) | Returns true (1), if x is less than y, else false (0) |
| x < y | Returns true (1), if x is less than y, else false (0) |
| eq(x, y) | Returns true (1), if x equals y, else false (0) |
| x = y | Returns true (1), if x equals y, else false (0) |
| and(x, y) | Returns true (1), if both x and y are true (i.e. not 0) |
| or(x, y) | Returns true (1), if at least one of both x and y is true (i.e. not 0) |
| ifelse(c, x, y) | Returns x, if condition c is true (i.e. not 0), else y |
| rand_u(x, y) | Random number, uniform distribution with minimum x and maximum y |
| rand_g(x, y) | Random number, Gaussian distribution with mean x and standard deviation y |
| nodata() | Returns tables's no-data value |
| isnodata(x) | Returns true (1), if x is a no-data value, else false (0) |
Parameters
| Name | Type | Identifier | Description | Constraints | |
|---|---|---|---|---|---|
| Input | Table | table, input | TABLE | - | - |
| Output | Result | table, output, optional | RESULT_TABLE | - | - |
| Result | shapes, output, optional | RESULT_SHAPES | - | - | |
| Options | Result Field | table field | FIELD | Select a field for the results. If not set a new field for the results will be added. | - |
| Field Name | text | NAME | - | Default: Calculation | |
| Formula | text | FORMULA | - | Default: f1 + f2 | |
| Add Field to Formula | choice, GUI | FIELD_SELECTOR | Convenient way to append a field number to the formula. Shows one all numeric fields with number, name and datatype overview. | Available Choices: Default: 0 | |
| Selection | boolean | SELECTION | - | Default: 1 | |
| Use No-Data | boolean | USE_NODATA | - | Default: 0 |
Command Line
Usage: saga_cmd table_calculus 1 [-TABLE] [-FIELD ] [-RESULT_TABLE ] [-RESULT_SHAPES ] [-NAME ] [-FORMULA ] [-SELECTION ] [-USE_NODATA ] -TABLE: Table table, input -FIELD: Result Field table field -RESULT_TABLE: Result table, output, optional -RESULT_SHAPES: Result shapes, output, optional -NAME: Field Name text Default: Calculation -FORMULA: Formula text Default: f1 + f2 -SELECTION: Selection boolean Default: 1 -USE_NODATA: Use No-Data boolean Default: 0