Matlab - Extract properties as array from object-array

Question

how do I extract an array of object properties from an object array (where each of the objects within that array has that property?)

Ex.:

classdef myClass
    properties
        myProperty = 1
    end
end

--

myObjectMatrix(1:1000)  = myClass()
myObjectMatrix(100:234).myProperty   % what I thought would work but results in lots of individual results

[myObjectMatrix(100:234)..myProperty] works, but only in one dimension. I need to use reshape() if I have more than one dimension to 'fold' my results back.

Is there a better way?

Thanks!

Tom Carpenter · Accepted Answer · 2015-06-07 14:59:17Z

Basically that code would act on each member in turn and return a separate answer, so in the end you only get a 1x1 output.

The solution in that example is to use arrayfun(), such as:

myObjectMatrix(1:1000)  = myClass()
output = arrayfun(@(x) x.myProperty,myObjectMatrix(100:234))

That would give you a 1x135 array containing the value of each of the myProperty member from each of the elements selected from the class array.

In arrayfun you give a function to perform on each element in the array and then the array to act on. In this case I created an anonymous function which simply accesses myProperty on x - where x will be each object in the array in turn.

It is important to note that the above will only work if the property is a single value, not a matrix/array. If it is an array then the output will be nonuniform, and you will have to do:

output = arrayfun(@(x) x.myProperty,myObjectMatrix(100:234),'UniformOutput', false)

In this case 'output' will be a cell array containing the value of the property of each class.

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