function g = commGSP_gft(A, signal, type)
% Returns Graph Fourier Transform (GFT) of a signal on the graph A
% INPUT:
%   A - (symmetric) matrix to decompose
%   signal - vector (length equal to size of A) representing graph signal
%   of size number_of_nodes x 1, or a set of signals organized in a matrix
%   of size number_of_nodes x number_of_signals
%   type - string equal to 'laplacian' for Laplacian-based GFT
%          or 'modularity' for modularity-based GFT;
%          if the GFT eigenvector matrix/basis is already available, then
%          instead of a string, type is equal to the eigenvector matrix U
% OUTPUT
%   g - vector of spectral GFT coefficients having
%       the same length as input signal x

if strcmp(type,'laplacian') || strcmp(type,'modularity')
    [U, ~] = commGSP_eig_implicit(A, type);
else
    U=type;
end
g=U'*signal;

end