Is there a way to perform queries on object collections?

Hi, I know I can use arrayfun to call a method on each object in an array, but is there a way to perform queries across the array?

This is a made up example, but if I have a class

MATLAB code
classdef Employee
properties
  salary = 0; %Set later
end

And I have an array of instances of this class

MATLAB code
staff = [employee1 employee2 employee3 ..... employeeN];

Is there an easy way I can write a query to get, say, the 3 Employees with the largest salarys?

Thanks for any help, just give me a shout if this isn't clear.

Tom.

Answer 1

[Darik]

Use comma separated list syntax

staff = [employee1 employee2 employee3 ..... employeeN];
salary = [staff.salary];
[~, i] = sort(salary, 2, 'descend');
top3 = staff(i(1:3))

Keep in mind that if you ever want to subclass your Employee class (into e.g. Secretary and Manager classes) you won't be able to store them all in the same array without converting them all into simple Employee objects.

[tombola]

That's brilliant, thanks a lot.

Is there any way to remove NaNs from the list please? So if salary is NaN then it doesn't get included in a "top3" or "bottom3" sort?

[tombola]

Hi, I've worked it out.

nanPositions=[isnan(salary)]

staff(nanPositions)=[]

salary(nanPositions)=[]

Then sort. Thanks a lot for the answer above.

Answer 2

[Sean de Wolski]

Instead of having each employee be its own variable ( like this ) have an employer class with employees as properties and salaries as properties.

There are many example available from the documentation for classdef.

[tombola]

Hi, I definitely need it done the way in the example thanks.