dynsys op• 資料種類:points → measurement
• 呼叫: import fullseye as fs; fs.ledger.dynsys_correlation_dimension(points, n_radii=24, r_lo=None, r_hi=None, max_points=4000, seed=0)(要直接呼叫實作,import mathops; mathops.dynsys_correlation_dimension(points, n_radii=24, r_lo=None, r_hi=None, max_points=4000, seed=0);從台帳取用則 opsmath.get("dynsys_correlation_dimension"))
Grassberger–Procaccia 關聯維數 —— `log C(r)` 的斜率。
> 以下的詳細說明為原文 —— 摘要與標題已翻譯。
`C(r) is the fraction of point pairs closer than r`; for a self-similar
set it grows like `r**D`, and *D* is read off the straight part of the
log-log plot (fitted on the middle 60 % of the radii, where the curve is free
of the small-`r noise floor and the large-r` saturation).
★Why this earns its place: unlike box counting it needs no grid, and its
answers are known for simple sets — a circle gives 1, a filled square
2, a Cantor set `log2/log3 = 0.6309`. It measures a different quantity
from the existing `fractal_dimension` (box counting), so the two are an
independent pair rather than two names for one number.
Returns a `measurement`: the fitted dimension.
Raises `ValueError`: fewer than 32 points; not a 2-D array; non-finite
input; a degenerate cloud (every point identical); a radius range that leaves
no pairs.
Limits: sub-sampled to *max_points* (pairs grow quadratically). ★The
dominant error is not the sub-sampling but the radius window: the
default range is the 1st-25th percentile of pair distances, and on a *bounded*
set its upper end runs into the boundary, where `C(r)` saturates and flattens
the slope. Measured on a unit square (true D = 2): 1.879 with the default
window and 1.873 / 1.879 / 1.871 at 400 / 1,500 / 3,000 points —— more points
do not help; narrowing the window to `r_lo=0.01, r_hi=0.1` gives 1.947
and `0.002 / 0.05` gives 2.050. Pass *r_lo* / *r_hi* explicitly when the
answer matters, and report the window with the number.
mathops 的每個運算子都先檢驗輸入再計算(不讓任何東西無聲通過):
• **complex 輸入一律 ValueError** —— 強制轉成 float64 會無聲丟掉虛部(numpy 只發一個 ComplexWarning,然後回傳一個「看似合理卻是錯的」實數)。請明確寫出 .real/.imag/abs(),或改用支援複數的 complexops。
• **含被遮罩元素的 masked array 一律 ValueError** —— 拒絕「剝掉遮罩直接使用下面原值」的隱式轉換。請明確選擇填補還是丟棄。
• **所有輸入中的 NaN/Inf 一律 ValueError**(明確給出個數後拒絕 —— 它會汙染整個結果)。
• 形狀嚴格:不對 1-D 與 2-D 做隱式提升或廣播(向量槽位收到矩陣、矩陣槽位收到向量都是 ValueError;請明確 reshape)。
• 尺寸上限:接受矩陣的運算子與 stat_histogram 的 bins,超過 mathops.MAX_ELEMENTS(2^26 ≈ 6700 萬個元素)即 ValueError。
• 範例資料目錄(下載 URL / 授權) —— 2-D 用 skimage.data(BSD/公有領域)加合成圖,3-D 給出真實資料源(Stanford/PDS 等)的下載 URL。
• 運算子來歷與參考文獻 —— 該運算子族所依據的研究/方法出處。
• 演算法的正典(作者・年份)與用途見上面的族使用指南。
• poc_what_a_picture_cannot_check — py -3.11 examples/poc_what_a_picture_cannot_check.py
measurement 作為輸入)—
dynsys)ode_flow_states · ode_vector_field_grid · dynsys_poincare_section · dynsys_lyapunov_spectrum · dynsys_bifurcation_map
*Provenance: mathops.py — MATH 運算子登記表。本條目由 tools/opdocs.py md 自動產生(請勿手動編輯)。*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.