VertConcatenated Parsing of Respective Function Outputs

Hi all I need a little help with syntax here, trying to vertically concatenate the respective outputs [c,ceq] from functions fcn1 and fcn2 below So [c,ceq] should be

c = [1;2;3;4] % concat of [1;2;] & [3;4]
ceq = [5;6] % concat of [] & [5;6]

For context, fcn will be a nonlinear constraint function for an fmincon, which can be comprised of potentially several fcn1,fcn2,fcn3.

all the best,

Mark

function [c,ceq] = TestFunctionDualOutputParsing

fcn = @(x) deal(fcn1(x),fcn2(x)); % doesn't work

[c,ceq] = fcn(1);

function [c1,ceq1] = fcn1(x)
c1 = [1;2].*x;
ceq1 = [].*x;

function [c2,ceq2] = fcn2(x)
c2 = [3;4].*x;
ceq2 = [5;6].*x;

Answer 1

[Guillaume]

Unfortunately, in matlab, there is no way to pass the second or later output of a function directly to another function. You have to use a temporary variable, which precludes doing it in an anonymous function. You don't have a choice but to implement it as a standard function:

function [c, ceq] = fcn(x)
  [c1, ceq1] = fcn1(x);
  [c2, ceq2] = fcn2(x);
  c = [c1; c2];
  ceq = [ceq1; ceq2];
end

[Mark Whirdy]

Due to my context of having multiple nonlinear constraints (which can be switched on/off according to other settings), concatenating the outputs in-function like this is not a solution for me.

[Guillaume]

Right, sorry I missed that you would have a varying number of function handles. The following will work:

function [out1, out2] = dispatch2output(x, varargin)
  [out1, out2] = cellfun(@(fn) fn(x), varargin, 'uni', false);
  out1 = vertcat(out1{:});
  out2 = vertcat(out2{:});
end

You call it with:

[c, ceq] = dispatch2output(x, @fcn1);
[c, ceq] = dispatch2output(x, @fcn1, @fcn2);
[c, ceq] = dispatch2output(x, @fcn1, @fcn2, @fcn3);

[Guillaume]

Finally, a generalisation of dispatch2output to any number of outputs:

function varargout = dispatchNoutput(x, varargin)
  fnouts = cell(1, nargout);
  [fnouts{:}] = cellfun(@(fn) fn(x), varargin, 'uni', false);
  varargout = cellfun(@(c) vertcat(c{:}), fnouts, 'uni', false);
end