# Model Expression

Segment objects from measurements using expressions and models.

## Parameters

### Expression

Write the expression for the segmentation, examples can be found below. The following comparators can be used for the expression:

Standard arithmetic (`+`

,`-`

,`/`

,`*`

…) and comparison operators (`=`

,`>`

,`<`

…) as well as some mathematical expressions (…) and constant values can be used in expressions.

### Model

Select model to apply to the expression.

### Min area

The minimum number of pixels for an object to be included.

### Max area

The maximum number of pixels for an object to be included.

If 0 no maximum area is defined.

### Object filter

Use an expression to further exclude unwanted objects based on shape.

Properties that can be used for the Expression:

`Area`

`Length`

`Width`

`Circumference`

`Regularity`

`Roundness`

`Angle`

`D1`

`D2`

`X`

`Y`

`MaxBorderDistance`

`BoundingBoxArea`

For details on each available property see: Object properties Details

### Shrink

Takes away numbers of pixels at the borders of the objects included in images.

### Link

Only visible when applicable

Link output objects from two or more segmentations to top segmentation. Descriptors can then be added to the common object output and will be calculated for objects from all segmentations.

The segmentations must be at same level to be available for linking.

## Examples

### Using class

Segment object classified to sample class. **Expression:** `class = sample`

### Using negative

Segment object not classified. **Expression: **`class != none`

### Band index comparison

Indexing with 1 based index in band list. Expression `(B10 > 1.5 or B15 < 2) and B20 <=1.2)`

Band names can also be used instead of band numbers in the example the band names are HE and LE. `HE > 20 and LE <40`

`HE`

and `LE`

are only applicable to X-Ray detectors e.g., Detection Technology camera

### Wavelength number

Using wavelength number. **Expression: **`(W980 > 1.5 or W1024 < 2) & W1200 <= 1.2`