This custom feature calculates the average area per spot in a cell by dividing the area of the cell through the number of spots in that cell. It is based on an analysis setup for an image with cells and spots. The class tree could look like this:

To create this custom feature you have to define the following operands and expression for the class Cell:

• Operand a:
• Class: Cell
• Feature: Area
• Operand b:
• Class: All Spots per Cell
• Feature: Count
• Define Custom Expression: a/b