seqcomp

seqcomp is an R package for anytime-valid sequential comparison of probabilistic forecasters, implementing the framework of Choe and Ramdas (2024). Given two competing forecasters and a sequence of binary or categorical outcomes, the package constructs confidence sequences and e-processes for the running mean score difference that are valid simultaneously at every point in time, without requiring a pre-specified sample size or adjustment for repeated monitoring. For three or more forecasters, seqcomp also implements Sequential Model Confidence Sets (Arnold, Gavrilopoulos, Schulz and Ziegel, 2026), which extend this guarantee to a running subset of models that have not yet been shown to underperform.

The package provides:

• Positively oriented proper scoring rules (Brier, logarithmic, spherical, CRPS, tick loss, QLIKE, Winkler).
• Anytime-valid confidence sequences: Hoeffding-style (Theorem 1, Choe and Ramdas 2024) and empirical Bernstein (Theorem 2).
• An asymptotic confidence sequence for unbounded scoring rules (Appendix C, Choe and Ramdas 2024).
• Sub-exponential e-processes for sequential hypothesis testing (Theorem 3).
• Winkler-score tools for one-sided sequential inference with unbounded binary scoring rules.
• Lag-handling utilities for multi-step-ahead forecast evaluation via stream splitting.
• Sequential Model Confidence Sets (SMCS) for evaluating three or more forecasters simultaneously, using closure-principle and joint-confidence- sequence constructions.
• Predictable-bounds tools for settings where score differences are not globally bounded in advance.

All boundary computations (normal mixture, gamma-exponential mixture, polynomial stitching) are implemented from scratch, with no dependency on the confseq package.

Installation

Available on CRAN:

install.packages("seqcomp")

The development version can be installed from GitHub:

# install.packages("pak")
pak::pak("alasgarliakbar/seqcomp")

Basic example

compare_forecasts() is the main entry point. It computes pointwise scores, the running mean score difference, a confidence sequence, and two one-sided e-processes in a single call.

library(seqcomp)

set.seed(1)
n <- 300
y <- rbinom(n, size = 1, prob = 0.55)

# Forecaster p has some signal; forecaster q always predicts 0.5
p <- ifelse(y == 1, 0.62, 0.38)
q <- rep(0.50, n)

out <- compare_forecasts(
  p            = p,
  q            = q,
  y            = y,
  scoring_rule = "brier"
)

tail(out[, c("t", "estimate", "lower", "upper", "e_pq", "e_qp")])
#>       t estimate      lower     upper    e_pq         e_qp
#> 295 295   0.1056 0.07129320 0.1399068 2681618 2.220446e-16
#> 296 296   0.1056 0.07140910 0.1397909 2824574 2.220446e-16
#> 297 297   0.1056 0.07152422 0.1396758 2975161 2.220446e-16
#> 298 298   0.1056 0.07163857 0.1395614 3133784 2.220446e-16
#> 299 299   0.1056 0.07175215 0.1394478 3300873 2.220446e-16
#> 300 300   0.1056 0.07186498 0.1393350 3476882 2.220446e-16

The column estimate is the running mean score difference $\hat{\Delta}t = \frac{1}{t}\sum{i=1}^{t}(S(p_i,y_i)-S(q_i,y_i))$. Positive values favour p; negative values favour q. The columns lower and upper are the empirical Bernstein confidence sequence bounds. The columns e_pq and e_qp are the two one-sided e-process values; the two-sided rejection threshold at level alpha = 0.05 is 2 / 0.05 = 40.

plot(
  out$t, out$estimate,
  type = "l",
  ylim = range(c(out$lower, out$upper, 0), finite = TRUE),
  xlab = "Time",
  ylab = "Running mean score difference"
)
lines(out$t, out$lower, lty = 2, col = "steelblue")
lines(out$t, out$upper, lty = 2, col = "steelblue")
abline(h = 0, col = "gray50")
legend(
  "topleft",
  legend = c("Estimate", "95% EB confidence sequence"),
  lty    = c(1, 2),
  col    = c("black", "steelblue"),
  bty    = "n"
)

Scale parameter conventions

Two scale conventions are used throughout, following Choe and Ramdas (2024) exactly. Theorem 1 (Hoeffding CS) requires $|\hat{\delta}_i| \leq c$, so c = 1 is used for Brier or spherical score differences in $[-1, 1]$. Theorems 2 and 3 (empirical Bernstein CS and e-process) require $|\hat{\delta}_i| \leq c/2$, so c = 2 is used for the same score differences. compare_forecasts() applies these conventions automatically. They differ from the Python comparecast package, which applies the Theorem 2/3 convention throughout.

Lower-level interface

compare_forecasts() is a convenience wrapper. The underlying functions can be called directly for finer control:

scores_p <- brier_score(p, y)
scores_q <- brier_score(q, y)

cs  <- cs_bernstein(scores_p, scores_q, alpha = 0.05, c = 2)
ep  <- eprocess(scores_p, scores_q, alpha = 0.05, c = 2)

Comparing more than two forecasters

For three or more candidate forecasters, use compare_multiple_forecasts(), which extends the same anytime-valid guarantees to a Sequential Model Confidence Set (SMCS):

out <- compare_multiple_forecasts(
  forecasts    = cbind(p1, p2, p3),
  outcomes     = y,
  scoring_rule = "brier"
)

tail(out$smcs_strong)

See the SMCS vignette for the strong and weak notions of superiority, and the closed-testing multiplicity correction. Or, access it locally via vignette("smcs", package = "seqcomp").

Background

The statistical methods in seqcomp are based on:

• Confidence sequences and time-uniform probability bounds (Howard, Ramdas, McAuliffe and Sekhon, 2021).
• E-values and game-theoretic statistics (Ramdas, Grünwald, Vovk and Shafer, 2023).
• Sequential forecaster comparison under the weak null hypothesis (Choe and Ramdas, 2024).
• Sequential model confidence sets for multi-model comparison (Arnold, Gavrilopoulos, Schulz and Ziegel, 2026).

The package was developed as part of a bachelor’s thesis at the Vienna University of Economics and Business (WU Vienna).

Citation

If this package is used in published work, please cite the package itself and the following papers:

citation("seqcomp")

References

Arnold, S., Gavrilopoulos, G., Schulz, B. and Ziegel, J. (2026). Sequential model confidence sets. Journal of the Royal Statistical Society Series B: Statistical Methodology, qkag066. https://doi.org/10.1093/jrsssb/qkag066

Choe, Y. J. and Ramdas, A. (2024). Comparing Sequential Forecasters. Operations Research, 72(4), 1368–1387. https://doi.org/10.1287/opre.2021.0792

Howard, S. R., Ramdas, A., McAuliffe, J. and Sekhon, J. (2021). Time-uniform, nonparametric, nonasymptotic confidence sequences. The Annals of Statistics, 49(2), 1055–1080. https://doi.org/10.1214/20-AOS1991

Howard, S. R., Ramdas, A., McAuliffe, J. and Sekhon, J. (2020). Time-uniform Chernoff bounds via nonnegative supermartingales. Probability Surveys, 17, 257–317. https://doi.org/10.1214/18-PS321

Ramdas, A., Grünwald, P., Vovk, V. and Shafer, G. (2023). Game-theoretic statistics and safe anytime-valid inference. Statistical Science, 38(4), 576–601. https://doi.org/10.1214/23-STS894

Waudby-Smith, I., Arbour, D., Sinha, R., Kennedy, E. H. and Ramdas, A. (2024). Time-uniform central limit theory and asymptotic confidence sequences. The Annals of Statistics, 52(6), 2613–2640. https://doi.org/10.1214/24-AOS2408