Triangle Simplex Plots for Representing and Classifying Heart Rate Variability

Mateusz Solinski*, Courtney Nicole Reed, Elaine Chew

*Corresponding author for this work

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Simplex plots afford barycentric mapping and visualisation of the ratio of three variables, summed to a constant, as positions in an equilateral triangle (2-simplex); for instance, time distribution in three-interval musical rhythms.

We propose a novel use of simplex plots to visualise the balance of autonomic variables and classification of autonomic states during baseline and music performance.

RR interval series extracted from electrocardiographic (ECG) traces were collected from a musical trio (pianist, violinist, cellist) in a baseline (5 min) and music performance (∼10 min) condition. Schubert’s Trio Op. 100, Andante con moto was performed in nine rehearsal sessions over five days. Each RR interval series’ very low (VLF), low (LF), and high (HF) frequency component power values, calculated in 30 sec windows (hop size 15 sec), were normalised to 1 and visualised in triangle simplex plots. Spectral clustering was used to cluster data points for baseline and music conditions.

We correlated the accuracy between the clustered and true values. Strong negative correlation was observed for the violinist (r = –0.80, p ≤ .01, accuracy range: [0.64, 0.94]) and pianist (r = –0.62, p = .073, [0.64, 0.80]), suggesting adaptation of their cardiac response (reduction between baseline and performance) over the performances; a weakly negative, non-significant correlation was observed for the cellist (r = –0.23, p = .545, [0.50, 0.61]), indi- cating similarity between baseline and performance over time. Using simplex plots, we were able to effectively rep- resent VLF, LF and HF ratios and track changes in autonomic response over a series of music rehearsals to ob- serve autonomic states and changes over time.
Original languageEnglish
Title of host publicationProceedings of Computing in Cardiology
PublisherIEEE Xplore
Number of pages4
ISBN (Electronic)979-8-3503-8252-5
Publication statusPublished - 21 Oct 2023
Event50th Computing in Cardiology Conference, CinC 2023 - Atlanta, United States
Duration: 1 Oct 20234 Oct 2023
Conference number: 50


Conference50th Computing in Cardiology Conference, CinC 2023
Abbreviated titleCinC 2023
Country/TerritoryUnited States
Internet address


  • representation
  • heart rate variability
  • ternary plot
  • simplex plot


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