% first, load the data
data = xff('*.ntt');

% then z-transform the third column (in our case) and take the 4th power
pdata = ztrans(data.Data(:, 3)) .^ 4;

% pre-detect beats
% since we used the 4th power, the skew detection threshold must be lowered
% and our signal has short spikes, so the detection length threshold also!
bp = heartbeats(pdata, struct( ...
    'skewdt',    0.05, ...
    'detlength', 0.01, ...
    'freq', 500));

% then pass this along with the actual signal back in
[bp, bs, bf, bv, cp, wgd, wd] = heartbeats(data.Data(:, 3), struct( ...
    'bppre',   bp, ...
    'cleanup', true, ...
    'freq',    500, ...
    'plot',    true));