Problem with using symbolic expersion in function toeplitz

I'm having some problems with the toeplitz function when using symbolic variables

syms a b c
toeplitz([a b c], [1 b/2 a/2])

I get the following error

Error using toeplitz (line 22)
Inputs must be numeric.

I'm using Matlab 2019b, I don't think this is a bug since when I open Matlab "toeplitz" function, it has that error call

Thanks in advance

[Francisco Williams]

update: I check the same function in Matlab 2019a and it worked. However I would like to find a workaround for the 2019b.

Answer 1

[madhan ravi]

Might be a bug. I didn’t have any problems with 2020a either. It’s better if you make a big report.

[Francisco Williams]

I create my own toepliz function. Which is basically the same that Matlab had I only commented the isnumeric condition.

That's why I was a bit reluctant to report it as a bug since in the Matlab function this condition appears.

function t = toeplitzPaco(c,r)
%TOEPLITZ Toeplitz matrix.
%   TOEPLITZ(C,R) is a non-symmetric Toeplitz matrix having C as its
%   first column and R as its first row.
%
%   TOEPLITZ(R) is a symmetric Toeplitz matrix for real R.
%   For a complex vector R with a real first element, T = toeplitz(r)
%   returns the Hermitian Toeplitz matrix formed from R. When the
%   first element of R is not real, the resulting matrix is Hermitian
%   off the main diagonal, i.e., T_{i,j} = conj(T_{j,i}) for i ~= j.
%
%   Class support for inputs C,R:
%      float: double, single
%      integer: uint8, int8, uint16, int16, uint32, int32, uint64, int64
%
%   See also HANKEL.

%   Thanks to A.K. Booer for the original version.
%   Copyright 1984-2017 The MathWorks, Inc.

%if ~(isnumeric(c) && (nargin < 2 || isnumeric(r)))
%    error(message('MATLAB:toeplitz:nonNumericInputs'));
%end

if nargin < 2
    c(1) = conj(c(1));                    % set up for Hermitian Toeplitz
    r = c;
    c = conj(c);
else
    if ~isempty(c) && ~isempty(r) && ~isequaln(r(1),c(1))
        warning(message('MATLAB:toeplitz:DiagonalConflict'))
    end
end

r = r(:);                               % force column structure
c = c(:);
p = length(r);
m = length(c);
x = [r(p:-1:2, 1) ; c];                 % build vector of user data
ij = (0:m-1)' + (p:-1:1);               % Toeplitz subscripts
t = x(ij);                              % actual data
if isrow(ij) && ~isempty(t)             % preserve shape for a single row
    t = t.';
end

[Francisco Williams]

That solved the problem btw

[madhan ravi]

This is one of the reasons that you SHOULD NOT name a function as same as the inbuilt function!

[Francisco Williams]

what? I didn't, I KNOW that. Check the name of the function toepliztPaco (that's my function). I just went inside the MAtlab toeplitz function copied and created my own function and commented the isnumeric condition.

As I MENTIONED in my last comment.

[Francisco Williams]

Update

toeplizt function can indeed take symbolic in Matlab 2019b. The problem I had was that I installed Maple and click on "link to Matlab" option. This option uses Maple symbolic solver and affects other Matlab functions.

I uninstalled Maple and then everything worked as it should. No need to create my own toeplitz function