How to include variable number of outputs on MATLAB System block in Simulink?

I have a MATLAB System block in Simulink and want to have different number of outputs depending on checkboxes inside the system block. So, I have followed these instructions ( https://ch.mathworks.com/help/simulink/ug/system-block-customizing-dialog.html ) and the checkboxes assign true or false variables (about whether a certain output should be output or not). But I can not get it to work with different numbers of outputs.

If you download this code, and open simulink and put in Matlab system and select it you get the block. But it can't change the number of outputs and gives an error when you open and close the block with different boxes ticked.

Thank you so much in advance! Let me know if there is anything else needed.

classdef test_varying_outputs < matlab.System

properties (Nontunable)

% Output1 Do you want to output another scalar?

Output1 (1,1) logical = false;

% Output2 Do you want to output a 2D vector?

Output2 (1,1) logical = false;

% Output3 Do you want to output a 3D vector?

Output3 (1,1) logical = false;

end

methods (Access = protected)

% Initialise states

function setupImpl(~)

end

% Set up output data

function data_type_out = getOutputDataTypeImpl(obj)

% Get outputs data type.

data_type_out = cell(1, getNumOutputs(obj));

for i = 1:getNumOutputs(obj)

data_type_out{i} = 'double';

end

end

function output_complex = isOutputComplexImpl(obj)

% Is output complex

output_complex = cell(1, getNumOutputs(obj));

for i = 1:getNumOutputs(obj)

output_complex{i} = false;

end

end

function size_out = getOutputSizeImpl(obj)

% Return sizes of outputs

size_out = cell(1, getNumOutputs(obj));

size_out{1} = [1 1];

out_ind = 2;

if obj.Output1

size_out{out_ind} = [1 1];

out_ind = out_ind + 1;

end

if obj.Output2

size_out{out_ind} = [2 1];

out_ind = out_ind + 1;

end

if obj.Output3

size_out{out_ind} = [3 1];

end

end

function varargout = isOutputFixedSizeImpl(obj)

% Get outputs fixed size.

varargout = cell(1, getNumOutputs(obj));

for i = 1:getNumOutputs(obj)

varargout{i} = true;

end

end

% Code that executes each step

function varargout = stepImpl(obj, ref, e)

varargout{1} = 4; % Output that is always on

out_ind = 2;

if obj.Output1

varargout{out_ind} = 2;

out_ind = out_ind + 1;

end

if obj.Output2

varargout{out_ind} = [4 5];

out_ind = out_ind + 1;

end

if obj.Output3

varargout{out_ind} = [3.2 3.3 3.4];

end

end

function resetImpl(~)

end

end

% Block icon and dialog customizations

methods (Static, Access = protected)

function header = getHeaderImpl

header = matlab.system.display.Header(...

'lmsSysObj', ...

'Title', 'different number of outputs');

end

function tabs = getPropertyGroupsImpl

group = matlab.system.display.SectionGroup(...

'Title', 'Outputs', ...

'propertyList',{'Output1','Output2','Output3'});

% Add a button that calls back into the visualize method

group.Actions = matlab.system.display.Action(@(actionData,obj)...

visualize(obj,actionData),'Label','Visualize');

tabs = group;

end

end

methods (Access = protected)

function icon = getIconImpl(~)

icon = sprintf('different number of outputs');

end

function [in1name, in2name] = getInputNamesImpl(~)

in1name = 'in1';

in2name = 'in2';

end

function varargin = getOutputNamesImpl(obj)

varargin{1} = 'out';

out_ind = 2;

if obj.Output1

varargin{out_ind} = 'out scalar';

out_ind = out_ind + 1;

end

if obj.Output2

varargin{out_ind} = "out 2x1";

out_ind = out_ind + 1;

end

if obj.Output3

varargin{out_ind} = 'out 3x1';

end

end

end

end

[Benjamin Campbell]

What I want to do is done in many blocks on simulink, for example the block LMS block, see below. Thanks!

Answer 1

[Balavignesh]

Hi Benjamin Campbell,

As per my understanding, you want to change the number of outputs in the MATLAB System block depending on the properties set.

As per the documentation of ”getNumOutputsImpl”, use “nargout” in “stepImpl” method when you have variable number of outputs. Please refer to the example below.

methods (Access = protected)
   function varargout = stepImpl(~,varargin)
      for i = 1:nargout
         varargout{i} = varargin{i}+1;
      end
   end
end

I hope this resolves your queries.

[Benjamin Campbell]

That worked thank you for the links and the help!