www.pudn.com > HHT_power-system_power-quality_disturbances-detect > toimage.m, change:2007-06-27,size:3003b

```%TOIMAGE  transforms a spectrum made of 1D functions in an 2D image
%
% [im,tt,ff] = TOIMAGE(A,f,t,splx,sply) transforms a spectrum made
% of 1D functions (e.g., output of "hhspectrum") in an 2D image
%
% inputs :   - A    : amplitudes of modes (1 mode per row of A)
%            - f    : instantaneous frequencies
%            - t    : time instants
%            - splx : number of columns of the output im (time resolution).
%                     If different from length(t), works only for uniform
%                     sampling.
%            - sply : number of rows of the output im (frequency resolution).
% outputs :  - im   : 2D image of the spectrum
%            - tt   : time instants in the image
%            - ff   : centers of the frequency bins
%
% Examples : [im,tt,ff] = toimage(A,f);[im,tt] = toimage(A,f,t);[im,tt,ff] = toimage(A,f,sply);
%            [im,tt,ff] = toimage(A,f,splx,sply);[im,tt,ff] = toimage(A,f,t,splx,sply);
%
%
%  emd, hhspectrum, disp_hhs
%
% G. Rilling, last modification 3.2007
% gabriel.rilling@ens-lyon.fr

function [im,tt,ff] = toimage(A,f,varargin)

DEFSPL = 400;

error(nargchk(2,5,nargin));

switch nargin
case 2
t = 1:size(A,2);
sply = DEFSPL;
splx = length(t);
case 3
if isscalar(varargin{1})
t = 1:size(A,2);
splx = length(t);
sply = varargin{1};
else
t = varargin{1};
splx = length(t);
sply = DEFSPL;
end
case 4
if isscalar(varargin{1})
t = 1:size(A,2);
sply = varargin{1};
splx = varargin{2};
else
t = varargin{1};
sply = varargin{2};
splx = length(t);
end
case 5
t = varargin{1};
splx = varargin{2};
sply = varargin{3};
end
if isvector(A)
A = A(:)';
f = f(:)';
end

if issparse(A) || ~isreal(A) || length(size(A)) > 2
error('A argument must be a real matrix')
end
if issparse(f) || ~isreal(f) || length(size(f)) > 2
error('f argument must be a real matrix')
end
if any(size(f)~=size(A))
error('A and f matrices must have the same size')
end
if issparse(t) || ~isreal(t) || ~isvector(t) || length(t)~=size(A,2)
error('t argument must be a vector and its length must be the number of columns in A and f inputs')
end
if ~isscalar(splx) || ~isreal(splx) || splx ~= floor(splx) || splx <= 0
error('splx argument must be a positive integer')
end
if ~isscalar(sply) || ~isreal(sply) || sply ~= floor(sply) || sply <= 0
error('splx argument must be a positive integer')
end

if any(diff(diff(t))) && splx ~= length(t)
warning('toimage:nonuniformtimeinsants','When splx differs from length(t), the function only works for equally spaced time instants. You may consider reformating your data (using e.g. interpolation) before using toimage.')
end

f = min(f,0.5);
f = max(f,0);

indf = round(2*f*(sply-1)+1);
indt = repmat(round(linspace(1,length(t),splx)),size(A,1),1);
im = accumarray([indf(:),indt(:)],A(:),[sply,splx]);

indt = indt(1,:);
tt = t(indt);
ff = (0:sply-1)*0.5/sply+1/(4*sply);

end```