ecg_axis.m

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% BRAVEHEART - Open source software for electrocardiographic and vectorcardiographic analysis
% ecg_axis.m -- Calculates frontal plane QRS axis
% Copyright 2016-2025 Hans F. Stabenau and Jonathan W. Waks
% 
% Source code/executables: https://github.com/BIVectors/BRAVEHEART
% Contact: braveheart.ecg@gmail.com
% 
% BRAVEHEART is free software: you can redistribute it and/or modify it under the terms of the GNU 
% General Public License as published by the Free Software Foundation, either version 3 of the License, 
% or (at your option) any later version.
%
% BRAVEHEART is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; 
% without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. 
% See the GNU General Public License for more details.
% 
% You should have received a copy of the GNU General Public License along with this program. 
% If not, see <https://www.gnu.org/licenses/>.
%
% This software is for research purposes only and is not intended to diagnose or treat any disease.
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function Raxis = ecg_axis(R1, S1, RF, SF)

RX = R1 - abs(S1);

% Correction for using the augmented unipolar lead and bipolar lead. See Novosel et al. Croat Med J. 1999 Mar;40(1):77-9. PMID: 9933900
RY = (2/sqrt(3)) * (RF - abs(SF));      

Raxis = atan2d(RY,RX);