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VertConcatenated Parsing of Respective Function Outputs

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Mark Whirdy
Mark Whirdy on 21 Sep 2014
Commented: Guillaume on 22 Sep 2014
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;

Answers (1)

Guillaume
Guillaume on 21 Sep 2014
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
  3 Comments
Guillaume
Guillaume on 22 Sep 2014
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

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