Exploring the Calculator Dialog Box - MapInfo_Pro_Advanced - 2023

Expressions

Expressions include standard mathematical and logical expressions. See Common expressions for more details.

Operators

The Operators drop-down list contains arithmetic operators (+, -), and comparison and logical operators (=, >, <) supported by the Calculator tool. You can use arithmetic and logical operators on single or multiple input raster files. See Arithmetic operators for more details.

Functions

Load

Click Load to load a previously saved expression in your computer. For example, if you have an expression (InputGrid1+InputGrid2)/2 saved in your computer, you can browse to the location of the file that contains the expression, select the file, and load it in the Expression Editor. Use this option for frequently used expressions.

Save

Click Save to save an expression in the Expression Editor to a location in your computer.

Validate

Click Validate to validate an expression entered in the Expression Editor. If an expression is valid, you will see a message confirming that the expression is valid.

Clear

Click Clear to clear an expression in the Expression Editor.

Expression Editor

Expression Editor is the place where you write your expressions. You can use [CTRL]+ [Space Bar] on your keyboard, to view suggestions while writing expressions. An alias name is assigned to each grid or value and is used to identify the item in the Expression Editor.

One major advantage of using an alias instead of the actual raster file name is that the same expression can be applied using different grids.

Inputs

In the Inputs section, you can perform the following:

• New - Click New to add a raster as operand. To add a second operand, click New again.
• Remove - Click Delete Row to delete a grid from the Inputs section.
• Insert - Click Insert to insert an alias in the Expression Editor. Click Insert again to insert a second alias in the Editor.

In case of multiple input files, one of the raster is primary raster. The primary raster will have a yellow star beside it. By default, the first raster in the Alias list is the primary raster. You can click on the white star beside the input alias to make it primary. The primary raster is used to define the properties such as geometry, projection, band data type etc., of the output file.

Click to browse to the location in your computer to open the raster.

Click to display the raster information in a window.

Variables

Create, insert, and delete variables that you will use to build an expression. For example, cond(Input_1 < Variable_1, Input_1, null), where Variable_1=20.

More Options

If required, expand More Options to set the following options.

• Override Output Field Type - Select this option to create output data in the specified raster type such as continuous, classified or imagery.
• Output Band Data Type - Select this option to create output data having specified band/stored data type. For example, if you select Automatic, output data type would be similar to input data type.
• Strict Null Handling - Select this option to create output data having NULL where input data is NULL. By default, it is true which means the NULL cells in the input raster will not be evaluated and will always be set to NULL in the output raster. If it is set to false, then the calculator expressions will be evaluated even for input raster cells with NULL values.
• Output Extent Covers Input - By default, it is true which means the calculator creates an output raster which has the same extents as the primary input raster. If it is set to false, it extends the output raster to cover all input rasters.
• Clip Extent - Instead of working on the entire raster, you can also perform calculation on a specific portion of the raster. Use one of the following options to specify the data extent that you want to perform the operation on.
  • Full Data Extent - This option denotes the complete extent of the input raster file. If you want to perform the calculation on the entire grid, select this option.
  • User Rectangle - Enter the rectangular bounds to define the portion of the raster. You can also draw a rectangle on the open map and the bounds get auto-populated.
  • Map Extent - Use map extent from the input raster file to define the portion of the raster.

Output as Classified

Select the Output as classified check-box if you want the output raster as a classified GRC or MRR. For more details, refer to Classified Output Support.

Output File

Specify a name, location and format for the output raster that you are creating. In the Output File box enter the name you want to specify for your output file. Click to browse to the location in your computer to save the output file. You can also select the required output file format.

Click Output Settings to specify the following. The values in Output Settings are controlled by the Raster Preferences dialog; however, you can override those settings here.

• Display Output File - Select the check-box, if you want to open the output file in the Map window on completion of the operation. You can configure to make this the default behavior from the Raster Preferences dialog.

  If the output file format is an MRR or a TIFF, additional options appear. The available options are listed below.

• Compression Settings
  • Data Balanced
  • Data Speed
  • Data Space
  • Advanced

  The Data Balanced option allows you to achieve a balance between speed of operation and file size. The system selects the best combination of speed and space for you. With the other two options Data Speed and Data Space, you can choose between speed of operation and storage space. Choose Advanced option to set the advanced compression settings such as compression method, level, and encoding type. For details on the Advanced option, see Compression Settings.

• Compression- Select a suitable compression method and level for the data. For more information on compression, see Compression methods.
• Encoding Type - Select a suitable Encoding Type for the data from the list. It enables you to compress the data when saving a raster to MRR format. Encoding Type is enabled only when the raster field type is Continuous and the compression method is lossless such as ZIP, LZMA or LZ4. The drop-down list contains the following:
  • None - No encoding.
  • Previous Column Linear - Performs linear estimation of the value from previous two columns.
  • Previous Column Value - Predicts the value from previous column.
  For more information, see Encoding Type.