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qfa

Quantile-Frequency Analysis (QFA) of Time Series and Spline Quantile Regression (SQR)

v5.0 · Mar 30, 2026 · GPL (>= 2)

Description

Implementation of quantile frequency analysis (QFA) for time series based on trigonometric quantile regression and of spline quantile regression (SQR) for estimating the coefficients in linear quantile regression models as smooth functions of the quantile level. References: [1] Li, T.-H. (2012). ''Quantile periodograms,'' J. of the American Statistical Association, 107, 765–776. <doi:10.1080/01621459.2012.682815> [2] Li, T.-H. (2014). Time Series with Mixed Spectra, CRC Press. <doi:10.1201/b15154> [3] Li, T.-H. (2025). ''Quantile Fourier transform, quantile series, and nonparametric estimation of quantile spectra,'' Communications in Statistics: Simulation and Computation, 1–22. <doi:10.1080/03610918.2025.2509820> [4] Li, T.-H. (2025). ''Quantile-crossing spectrum and spline autoregression estimation,'' Statistical Inference for Stochastic Processes, 28, 20. <doi:10.1007/s11203-025-09336-7> [5] Li, T.-H. (2025). ''Spline autoregression method for estimation of quantile spectrum,'' J. of Computational and Graphical Statistics, 1-15. <doi:10.1080/10618600.2025.2549452> [6] Li, T.-H., and Megiddo, N. (2026). ''Spline quantile regression,'' J. of Statistical Theory and Practice, 20, 30. <doi:10.1007/s42519-026-00545-8> [7] Li, T.-H. (2026). ''Spline quantile regression with cubic and linear smoothing splines,'' <doi:10.48550/arXiv.2603.22408>.

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CRAN Check Status

13 OK
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r-devel-linux-x86_64-debian-gcc OK
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r-devel-linux-x86_64-fedora-gcc OK
r-devel-windows-x86_64 OK
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Check History

OK 14 OK · 0 NOTE · 0 WARNING · 0 ERROR · 0 FAILURE Mar 10, 2026

Code

Structure

Lines of code

6,725

Files

55

Compiled share

2.8%

Has compiled src

Yes

Language breakdown

R 4,614 (68.6%)C/C++/src 186 (2.8%)Docs 1,925 (28.6%)

API

Exported functions

36

Internal functions

13

Recent export changes

v5.0+5 boot.sqr, sqr.plot, sqr1.fit +2 more
v4.0+5 sqdft, sqdft.fit, sqr +2 more

Testing & CI

Has tests

No

Test-to-code ratio

0.00

testthat edition

CI present

No

CI type

[]

PR gated

No

Docs

Return-value doc rate

100%

\dontrun example ratio

0%

Roxygen coverage

100%

Has pkgdown

No

NEWS present

No

Health & Security signals

Informational signals; not verdicts.

on.exit coverage

33.3%

Unsafe pattern score

0

Dep constraint coverage

0%

Secret pattern count

0

Bundled 3rd-party code

2 items

Portability & License

Min R version

3.5

System requirements

C++ standard

License

GPL (>= 2)

License flags

SPDX valid, OSI approved

History

Versions

9

First release

2013-06-13

Latest release

2026-03-30

Avg cadence

140 days

Cold removal rate

100%

Dep drift

21

LOC over versions

v0.0-10: 2,782 LOCv1.2: 1,774 LOCv2.0: 3,867 LOCv2.1: 3,938 LOCv3.1: 3,495 LOCv4.0: 4,955 LOCv4.1: 5,012 LOCv4.2: 5,051 LOCv5.0: 6,725 LOC

Per-file churn detail lives in the source pipeline: https://github.com/r-observatory/cran-code-metrics.

Dependency Network

Dependencies Reverse dependencies RhpcBLASctl doParallel fields foreach Matrix SparseM mgcv nlme quantreg colorRamps MASS osqp piqp boot qfa

Version History

10 tracked
updated 5.0 ← 4.2 diff Mar 30, 2026
new 4.2 Mar 10, 2026
updated 4.2 ← 4.1 diff Sep 10, 2025
updated 4.1 ← 4.0 diff Apr 8, 2025
updated 4.0 ← 3.1 diff Jan 7, 2025
updated 3.1 ← 2.1 diff Dec 19, 2024
updated 2.1 ← 2.0 diff Aug 20, 2023
updated 2.0 ← 1.2 diff May 16, 2023
updated 1.2 ← 0.0-10 diff Jan 17, 2023
new 0.0-10 Jun 20, 2013