function peaks = localpeaks(x,mode)
%LOCALPEAKS  Find local peaks and troughs in a vector
%
%   This function returns the indices of local peaks and/or troughs in a
%   vector.
%
%   PEAKS = IOSR.DSP.LOCALPEAKS(X) locates the local peaks in vector X.
%
%   PEAKS = IOSR.DSP.LOCALPEAKS(X,MODE) locates local features specified by
%   mode, which can be set to 'peaks' (default), 'troughs' in order to
%   identify local troughs, or 'both' in order to identify both local peaks
%   and troughs.

%   Copyright 2016 University of Surrey.

    assert(isvector(x), 'iosr:localpeaks:invalidX', 'Input must be a vector')

    if nargin < 2
        mode = 'peaks';
    end

    switch lower(mode)
        case 'peaks'
            % do nothing
            peaks = find_peaks(x);
        case 'troughs'
            peaks = find_peaks(-x);
        case 'both'
            peaks = find_peaks(x) | find_peaks(-x);
        otherwise
            error('iosr:localpeaks:unknownMode','Unknown localpeak mode. Please specify ''peaks'', ''troughs'' or ''both''');
    end

end

function peaks = find_peaks(x)
%FIND_PEAKS find local peaks in a vector

    peaks = false(size(x));
    peaks(2:end-1) = sign(x(2:end-1)-x(1:end-2)) + sign(x(2:end-1)-x(3:end)) > 1;

end