complex op• Data kinds: cimage → measurement
• Call: import fullseye as fs; fs.ledger.cplx_cr_residual(f, spacing=1.0) (to call the implementation directly, import mathops; mathops.cplx_cr_residual(f, spacing=1.0); from the registry, opsmath.get("cplx_cr_residual"))
Cauchy-Riemann residual of a sampled complex field — "is this field holomorphic?" as a number.
With f = u + i v sampled on a uniform grid, holomorphy means u_x = v_y and u_y = -v_x (Cauchy-Riemann). This returns the relative residual max(|u_x - v_y|, |u_y + v_x|) / max|grad| (central differences, numpy.gradient): 0 = the samples satisfy CR to the discretisation limit, 2 = the field is the conjugate of a holomorphic one (conj(z) gives exactly 2), values in between = partly analytic or noisy.
Grid convention (it decides the sign of the answer): f[i, j] is the field at z = x0 + j*spacing + i*spacing*1j — rows index the *increasing imaginary* axis, columns the real axis. Image arrays usually run rows *downward*; feeding one directly measures the conjugate field, whose residual is 2, not 0. Flip rows (f[::-1]) to use image data.
Discretisation, honestly: central differences are exact for polynomials of degree <= 2, so f = z**2 returns exactly 0; for higher order the residual floors at O(h^2 * |f'''|) (measured: f = z**3 on a [-1,1]^2 grid returns 1.7e-3 at h and 4.2e-4 at h/2 — a factor 4.00, the expected second order). Read a small value as "consistent with holomorphic at this resolution", never as proof.
A constant field returns 0.0 (it is holomorphic; the 0/0 of the normalisation is resolved by that limit, and stated here rather than left to numpy).
Raises ValueError: not a 2-D array, either dimension below 3 (no central difference exists), non-finite/masked input, over-cap size, non-finite or non-positive *spacing*.
HALCON: no operator (derivate_gauss supplies the real-valued derivatives one would build this from).
Every mathops op validates its input before computing (nothing slips through silently):
• complex input raises ValueError — coercing to float64 silently discards the imaginary part (numpy only emits a ComplexWarning and returns a plausible-looking wrong real number). State .real/.imag/abs() explicitly, or use complexops, which handles complex data.
• masked arrays with masked elements raise ValueError — the implicit conversion that peels off the mask and uses the raw values underneath is refused. Say explicitly whether to fill or to drop.
• NaN/Inf raises ValueError on every input (refused with the count stated — it propagates through the whole result).
• Shapes are strict: 1-D and 2-D are never implicitly promoted or broadcast (a matrix in a vector slot, or a vector in a matrix slot, raises ValueError; reshape explicitly).
• Size cap: ops that take a matrix, and the stat_histogram bins, raise ValueError beyond mathops.MAX_ELEMENTS (2^26 ≈ 67 million elements).
• Sample-data catalog (download URLs / licences) — 2-D uses skimage.data (BSD/public domain) plus synthetic images; 3-D lists download URLs for real data sources (Stanford, PDS, …).
• Operator provenance and references — the sources of the research/methods this op family came from.
• The canonical algorithm (author, year) and its uses are named in the family usage guide above.
• math_complex — py -3.11 examples/math_complex.py
• poc_complex_plane_fields — py -3.11 examples/poc_complex_plane_fields.py
measurement as input)—
complex)cplx_contour_circle · cplx_poly_eval · cplx_contour_integral · cplx_winding_number · cplx_cauchy_value · cplx_argument_principle · cplx_laurent_coeffs · cplx_joukowski
*Provenance: mathops.py — MATH operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.