MATLAB: How to measure the real size of a variable in workspace

MATLABpointerramsize;variablewhosworkspace

How to measure the real size of a variable in workspace?

When using handle objects I only see 8 Bytes while using the command 'whos'.

Best Answer

You only see 8 Bytes while using 'whos' because this is the size of the pointer as a reference to the handle object.

To evaluate the size of a variable with such a reference, please use the command 'struct' onto this variable.

This produces a minimal overhead to the real size, but doing this you can figure out the order of magnitude of the variable.

This means image you have a variable called 'a' which shows only 8 Byte via 'whos', then do the following:

>> b = struct(a);

If you use 'whos' right now, you will see a better scale of the size of 'a' in variable 'b'.

Related Solutions

MATLAB: Does “setVariable” in Simulink Test not update variables

In R2019b, the behavior of "setVariable" is modified such that it overrides only model variables (as opposed to MATLAB variables).

I attached a simpler model ("SimpleVars_R2019b.slx") to help illustrate this. This model has two "From Workspace" blocks, one set to "a" and one set to "evalin('base', 'b')".

If you call "findVars" on this model, only "a" is considered to be a model variable, even though both output their timeseries when run:

>> vars = Simulink.findVars('SimpleVars_R2019b')
vars = 
    VariableUsage with properties:
            Name: 'a'
          Source: 'base workspace'
      SourceType: 'base workspace'
           Users: {'SimpleVars_R2019b/From↵Workspace'}

The R2019b behavior provides stricter control of overrides and achieves parity with other Simulink tools. You will need to update the model to use variables which are recognized by Simulink.

Please update the "From Workspace" block variable parameter from "evalin('base', 'y_coordinate')" to just "y_coordinate". Then save the model and run the test file again.

You should observe that "setVariable" updates all of the variables now.

MATLAB: Do I get the error “Invalid default value for property” when trying to define one default instance variable value in terms of another

It is easier to see the reason for this issue once you fully-qualify the name of an instance variable with which you are defining another.

e.g.

classdef Example
    properties
        A = {'a','b','c'}
        B = [Example.A,'d']
    end
end

yields the error

>> Example

Invalid default value for property 'B' in class 'Example':

The property 'A' in class 'Example' must be accessed from a class instance because it is not a Constant property.

Because 'B' is defined in terms of A, we must either define 'A' to be a "Constant" property or we must initialize B in the constructor.

i.e.

classdef Example
    properties (Constant)
        A = {'a','b','c'}
    end
    properties
        B = [Example.A,'d']
    end
end

classdef Example
    properties
        A = {'a','b','c'}
        B
    end
    methods
        function obj = Example()
            obj.B = [obj.A,'d'];
        end
    end
end

Best Answer

Related Solutions

MATLAB: Does “setVariable” in Simulink Test not update variables

MATLAB: Do I get the error “Invalid default value for property” when trying to define one default instance variable value in terms of another

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