Click the Set Operation Expression button on the Algebraic Operation window to enter the Raster Algebraic Operation Expression dialog.
In the Raster Algebraic Operation Expression dialog box, the operation expression can be entered semi-automatically. The Parameter Description of the dialog box is as follows:
Workspace
The All Data source in the Current Workspace and the Dataset under the Datasource are listed in the Workspace on the left, and Band Info can be displayed under the Image Dataset node. It is convenient for you to quickly select the Raster Dataset or band to be input when inputting the operation expression.
Common Functions
Common Functions include Arithmetic, Trig, Exp/Log and other functions. The contents of each function will be described in detail below.
| Type of operation | Explain | Illustration |
| Arithmetic function | abs(x) | Absolute value function. |
| mod(x, y) | The modulo function, which finds the remainder of X/y, has an integer value as its output. Mod (X, y) = X for y > X. | |
| floor(x) | The RoundDown function, which gets the smaller integer nearest to X (for example, 1.8 is rounded down to 1.0, and -2.2 is rounded down to -3.0), outputs a floating-point value. | |
| Trig | sin(x) | Sine function |
| cos(x) | Cosine function | |
| tan(x) | Tangent function | |
| cot(x) | Cotangent function | |
| asin(x) | Arcsine function | |
| acos(x) | Arccosine function | |
| atan(x) | Arctangent function | |
| acot(x) | Arccotangent function | |
| sinh(x) | Hyperbolic sine function | |
| cosh(x) | Hyperbolic cosine function | |
| tanh(x) | The hyperbolic tangent function | |
| Exp/Log function | exp(x) | Function with the natural logarithm e as a power. |
| pow(x, y) | X to the y-th power. | |
| sqrt(x) | Square root of X. | |
| ln(x) | Take the natural logarithm. | |
| log(x) | Take the base 10 logarithm. | |
| Other functions | Con(x, y, z) | Conditional judgment function. X is the conditional expression (or value), and y and Z are the extracted values. If the function satisfies the condition X, the y value is extracted, otherwise the Z value is extracted. |
| IsNull(x) | Check whether the expression contains an invalid value. If X is Null (that is, an invalid value), the return value is 1. Otherwise, the return value is 0. | |
| pick(n1,n2,n3,...,nn) | Update the grid values. The grid value of the first specified Raster Dataset is used as the corresponding position, and the grid value of the corresponding position is assigned according to the grid value of the subsequently input Raster Dataset or the input numerical value, and finally a new Raster Dataset is generated. |
Common Operators
Common Operators provided by SuperMap include basic arithmetic operators, relational operators and logical operators, as shown in the following figure. Click the button where the operator is located to display the corresponding Operator in the upper expression dialog box. For detailed instructions, see Common Operator
Expression input box
When a Dataset or operator is selected in Workspace (double-click), Common Functions (click), or Common Operators (click), the selection is displayed in the expression input box.
Caution: - Dataset, when
- referenced as an operation operand, is of the form Datasource _ name.Dataset _ name, For example, the reference of BeijingTerrain Dataset in Datasource Jingjin is: Jingjin. BeijingTerrain. The operand of an
- arithmetic operator can be a Dataset or a numeric constant. The argument of
- Math can be a numeric value, a Dataset, or the operation expression of a Dataset or multiple Datasets.
- Negative numbers are enclosed in parentheses (). The
- expression must contain at least one Raster Dataset.
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