dynare/matlab/get_variables_and_parameters_in_expression.m

function objects = get_variables_and_parameters_in_expression(expr)

% Returns the variables and parameters appearing in an expression.
%
% INPUTS
% - expr       [char]             1×m char array, dynare model expression (typically RHS or LHS of an equation).
%
% OUTPUTS
% - objects    [cell]             cell of row char arrays, names of the variables and parameters in expr.

% Copyright © 2020-2022 Dynare Team
%
% This file is part of Dynare.
%
% Dynare is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% Dynare is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with Dynare.  If not, see <https://www.gnu.org/licenses/>.

if iscell(expr)
    objects = splitexpr(expr{1});
    for i=2:length(expr)
        objects = [objects, splitexpr(expr{i})];
    end
else
    objects = splitexpr(expr);
end

% Filter out the numbers, punctuation.
objects(cellfun(@(x) all(isstrprop(x, 'digit')+isstrprop(x, 'punct')), objects)) = [];

% Filter out functions
objects(cellfun(@(x) ismember(x, {'log', 'log10', 'ln', 'exp', 'sqrt', 'abs', 'sign', 'sin', 'cos', 'tan', 'asin', 'acos', 'atan', 'min', 'max', 'normcdf', 'normpdf', 'erf', 'diff', 'adl'}), objects)) = [];

% Filter out empty elements.
objects(cellfun(@(x) all(isempty(x)), objects)) = [];


function o = splitexpr(expr)
o = strsplit(expr, {'+','-','*','/','^', '(', ')', ',', '\n', '\t', ' '});