FINDZEROEXTREMA1D - Find extremas and/or zero-crossings of 1D signals.

Contents

Description

Wrapping function for popular Matlab functions calculating extremas and/or zero-crossings of 1D signals.

Syntax

[Max, Min] = FINDZEROEXTREMA1D(S);
[Max, Min, Zero] = FINDZEROEXTREMA1D(S, x, met_extrema, met_zeros, D);

Inputs

S : input 1D signal.

x : (optional) domain coordinates of the input signal; default: x=[], ie. the natural coordinates (1:length(S)) are considered.

met_extrema : (optional) string defining the function used to compute the extrema of the signal; it is any of the following strings:

default: met_extrema='local5'.

met_zeros : (optional) string defining the function used to compute the zero-crossings of the signal; it is any among those strings: 'local3', 'findextrema' or 'crossing'; see below for the corresponding functions; default: met_zeros='local3'.

D : (optional) vector storing the variables [delta mindelta absval] (in this order) used simultaneously for finding extrema and zero-crossings when (see above) the method met_extrema is any among: 'local3', 'morph', 'local5', 'peakfinder', 'peakdet', 'fpeak', and/or when the method met_zeros is any among 'local3', 'morph'; a point is considered a peak if:

a point is considered a zero-crossing if:

default: D=[], ie. no restriction.

Outputs

Min, Max : matrix storing consisting of two columns; the first column contains the coordinates of the extrema positions, and column 2 contains the found values; in the case x=[] or x=(1:length(X)), the first column is in fact the indices of the extrema positions in the input signal; note moreover that in the case met_extrema='fpeak', the minima and maxima are stored together in the matrix Max (Min is therefore empty).

Zero : coordinates (or indices) of the zero-crossings.

Acknowledgment

The external functions called by FINDZEROEXTREMA1D are:

See also

Ressembles: PEAKFINDER, PEAKDET, FINDEXTREMA, EXTREMA, CROSSING, FIND. Requires: FINDZEROEXTREMA1D_BASE.

Function implementation

function [Max, Min, Zero] = findzeroextrema1D(S, varargin)

parsing parameters

error(nargchk(1, 15, nargin, 'struct'));
error(nargoutchk(0, 3, nargout, 'struct'));

% mandatory parameter
if ~isnumeric(S) || nb_dims(S)~=1
    error('findzeroextrema1D:inputerror','a 1D signal is required in input');
end

% optional parameters
p = createParser('FINDZEROEXTREMA1D');   % create an instance of the inputParser class.
p.addOptional('x', [], @(x) isempty(x) || (isnumeric(x) && nb_dims(x)==1));
p.addOptional('met_extrema','local5', @(x) isempty(x) || (ischar(x)&& ...
    any(strcmpi(x,{'ecke','local3','local5','findextrema','extrema', ...
    'peakfinder','fpeak','peakdet','morph'}))));
p.addOptional('met_zeros','local3', @(x) isempty(x) || (ischar(x)&& ...
    any(strcmpi(x,{'local3','naive','findextrema','crossing','morph'}))));
p.addOptional('delta', [], @(x) isempty(x) || ...
    (length(x)<=3 && isfloat(x) && all(x>=0)));

% parse and validate all input arguments
p.parse(varargin{:});
p = getvarParser(p);

setting internal variables

if ~isempty(p.met_extrema) && ~any(strcmpi(p.met_extrema,{'local3','local5','ecke','morph'})) && ...
    ~exist(p.met_extrema,'file')
    error('findzeroextrema1D:unknown', ...
        ['unknown method/function ' met_extrema]);
elseif ~isempty(p.met_zeros) && ~any(strcmpi(p.met_zeros,{'local3','naive','morph'})) && ...
    ~exist(p.met_zeros,'file')
    error('findzeroextrema1D:unknown', ...
        ['unknown method/function ' met_zeros]);
end

if ~isempty(p.x) && ~isequal(size(p.x),size(S))
        error('findzeroextrema1D:inputerror', ...
            'signal and signal''s coordinates must have same dimension');
elseif isempty(p.x)
    p.x = (1:length(S));
end

if isempty(p.delta),  p.delta = [0.5 0.1 0.1 0];  end

main computation

if nargout<3 && (nargout~=0 || ~p.disp)
    [Max, Min] = findzeroextrema1D_base(S, p.x, ...
        p.met_extrema, p.met_extrema, [], p.delta);
else
    [Max, Min, Zero] = findzeroextrema1D_base(S, p.x, ...
        p.met_extrema, p.met_extrema, p.met_zeros, p.delta);
end

Zero = nonzeros(Zero);

display

if p.disp
    figure, plot(p.x, S, 'x-'), hold on, grid on;
    plot(Max(:,1), Max(:,2), 'ro');
    if ~isempty(Min),  plot(Min(:,1), Min(:,2), 'gx');  end
    title(['extrema found using ' p.met_extrema]);
    if exist('Zero','var') && ~isempty(Zero)
        figure, plot(p.x, S, 'x-'), hold on, grid on;
        plot(Zero(:,1), S(Zero(:,1)), 'ro');
        title(['zero-crossings found using ' p.met_zeros]);
    end
end

end % end of findzeroextrema1D