A four-state Poincaré return map for heart-rate variability that derives its own statistics — SD1, SD2 and their ratio measured in the 45°-rotated frame, an ellipse drawn from exactly those two numbers about the cloud's centroid, and pairs formed only from beats the recording's own clock agrees are successive.
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status="ready" · a simulated five-minute supine baseline — 314 intervals in, 307 successive pairs plotted, two intervals unreadable and two neighbouring pairs refused because the clock says an ectopic beat was edited out between them. SD1, SD2 and their ratio are measured from the RR series itself, and the ellipse is those two numbers drawn one SD each about the cloud's own centroid. From 3:00 the subject breathes to a six-per-minute metronome: those pairs are picked out in their own tone, and the arm they form runs along the identity line rather than across it — the window reads SD2 142.4 ms against the recording's 99.4 ms, while its SD1, 44.8 ms, sits a couple of milliseconds off the overall 42.3 ms. Point at the cloud, or Tab to it and use the arrow keys, to read any pair off both axes.
Morning HRV · supine baseline
M. Okonkwo · 26 y · 8 Aug 2026 · supine · 5 min · spontaneous then paced breathing · Polar H10 · 1000 Hz
307 successive pairs · mean RR 946 ms · 63 bpm · ellipse area 13,217 ms²
SD1
42.3 ms
beat-to-beat width
SD2
99.4 ms
long-term length
SD1 : SD2
0.43
cloud shape
1,105 ms → 1,055 ms · -50 ms · pair 307 of 307 at 5:01
307 beat pairs
paced breathing · 6 / min · 123 pairs
SD1 × SD2 ellipse · 1 SD
line of identity
Centroid
mean RR 946 ms · 63 bpm · ellipse area 13,217 ms²
paced breathing · 6 / min
SD1 44.8 ms · SD2 142.4 ms · mean RR 940 ms
2 intervals came back unreadable and are in no figure on this card. 2 neighbouring pairs would have straddled a gap in the recording — the clock says those beats are not successive, so no dot was placed for them.
Each dot is one interval against the one that followed it. A metronomic heart would collapse the whole cloud onto the dashed identity line, so the width across that line is the beat-to-beat variation: SD1 is the standard deviation of the pairs measured perpendicular to the line — exactly SDSD ÷ √2 — and SD2 the standard deviation measured along it. The ellipse is those two numbers, one SD on each axis, drawn about the cloud's own centroid; its area is π · SD1 · SD2. A round cloud, SD1 : SD2 near 1, is usually artefact rather than a healthy heart. Point at the cloud, or tab in and use the arrow keys, to read any pair.
Morning HRV · supine baseline — 307 successive interval pairs. SD1 42.3 ms, SD2 99.4 ms, ratio 0.43, mean RR 946 ms (63 bpm). One row per 20 pairs.
Time
RR n
RR n+1
Change
Window
0:02
964 ms
1,034 ms
+70 ms
—
0:21
982 ms
898 ms
-84 ms
—
0:42
988 ms
979 ms
-9 ms
—
1:01
927 ms
896 ms
-31 ms
—
1:23
905 ms
870 ms
-35 ms
—
1:42
936 ms
1,020 ms
+84 ms
—
2:01
993 ms
927 ms
-66 ms
—
2:19
882 ms
885 ms
+3 ms
—
2:40
956 ms
894 ms
-62 ms
—
2:59
891 ms
961 ms
+70 ms
—
3:21
1,097 ms
1,018 ms
-79 ms
paced breathing · 6 / min
3:40
1,081 ms
1,059 ms
-22 ms
paced breathing · 6 / min
3:59
1,031 ms
1,087 ms
+56 ms
paced breathing · 6 / min
4:17
941 ms
1,031 ms
+90 ms
paced breathing · 6 / min
4:36
790 ms
876 ms
+86 ms
paced breathing · 6 / min
4:55
806 ms
814 ms
+8 ms
paced breathing · 6 / min
status="empty" · a valid contract with no intervals at all, worded so it cannot be mistaken for a failed fetch — and it says what the plot needs instead, because a stored RMSSD cannot be unrolled back into the cloud it came from.
Morning HRV · supine baseline
M. Okonkwo · 26 y · 8 Aug 2026 · supine · 5 min · spontaneous then paced breathing · Polar H10 · 1000 Hz
Every interval against the one after it, with an SD1 × SD2 ellipse fitted to the cloud
Not enough successive intervals
A Poincaré plot is built from beats that follow one another, so it needs at least 4 usable intervals in a row. One RMSSD, one SDNN — a summary cannot be unrolled back into the cloud it was computed from.
status="loading" · a skeleton holding the readout row and a square plot, with a comet silhouette lying inside a tilted ellipse so the card does not jump when the recording lands. aria-hidden, honouring prefers-reduced-motion, and no timer involved.
Morning HRV · supine baseline
M. Okonkwo · 26 y · 8 Aug 2026 · supine · 5 min · spontaneous then paced breathing · Polar H10 · 1000 Hz
Every interval against the one after it, with an SD1 × SD2 ellipse fitted to the cloud
Loading the Poincaré plot
status="error" · the fetch failed. Try again only appears when onRetry is passed, and clicking it flips the card to ready.
Morning HRV · supine baseline
M. Okonkwo · 26 y · 8 Aug 2026 · supine · 5 min · spontaneous then paced breathing · Polar H10 · 1000 Hz
Every interval against the one after it, with an SD1 × SD2 ellipse fitted to the cloud
Zyeon UI