Combine properties

Combine properties, categories, or descriptors using expression to calculate new properties and display them in the table view. The descriptor needs to be located at the same level in the Analyse Tree as the properties, categories, or descriptors that are supposed to be calculated.

Parameters

Expression

Write the expression for which properties to combine.

Standard arithmetic (+,-,/,* …) and comparison operators (=,>,< …) as well as some mathematical expressions (…) and constant values () can be used in expressions.

Expand to see all available operator

Arithmetic Operator	Description
`-`	Subtract
`+`	Add
`/`	Divide
`*`	Multiply
`%`	Modulo
`^`	Raised to a power

Comparison Operator	Description
`=`	Equal to
`\|` `OR`	TRUE if any of the conditions separated by OR is TRUE
`&` `AND`	TRUE if all the conditions separated by AND is TRUE
`!=` `<>`	Not equal to
`<`	Less than
`<=`	Less than or equal to
`>`	Greater than
`>=`	Greater than or equal to

Function operator	Description
`SQRT(N)`
`SIN(N)`
`COS(N)`
`EXP(N)`
`LOG(N)`
`LOG10(N)`
`AVG(N)`
`ROUND(N)`

Constants	Description
`TRUE`	Always evaluates to TRUE
`FALSE`	Always evaluates to FALSE
`INF`	token value
`PI`	approximated to 3.14159

The spatial parameters that can be used:

Area
Length
Width
Circumference
Regularity
Roundness
Angle
D1
D2
X
Y
MaxBorderDistance
BoundingBoxArea

For details on each available property see: Object properties Details

You can also use descriptors such as classification or quantification models. To make sure that no conflict is created always use an alias on the descriptors you want to use.

User-defined categories or properties using “Add Variable Id” can also be used just to write the header of the categories/properties.

Other expressions that can be used are bands or wavelengths to create you can find examples of them in the example section.

Type

Object
- Applies the expression on objects.
Pixel
- Applies the expression on individual pixels.

Smooth

Smooth prediction result using median filter kernel

None
- No Smoothing prediction.
Low
- Smoothing using median filter kernel with 5x5 pixel box
Medium
- Smoothing using median filter kernel with 10x10 pixel box
High
- Smoothing using median filter kernel with 15x15 pixel box

Examples

Properties

Expression:

(property1 + property2) * property3

Spatial descriptor

Expression:

circumference / area

(y / length) + (x / width)

Band

Indexing with 1 based index in band list. If band name can also be used instead of band number

Expression:

(b10 + 1.5)/ b15

Wavelength

Get band by using wavelength number

Expression:

(w980 + 1.5) / w1024