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.
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