scFPCDE

scFPCDE tests for differential gene expression along single-cell pseudotime using functional principal component analysis (FPCA). The package provides functions for fitting smooth expression trajectories, tuning smoothing parameters, running permutation-based D- and F-tests, and visualizing fitted gene curves.

Installation

Install the development version from GitHub:

# install.packages("remotes")
remotes::install_github("NLM-DIR/scFPCDE", build_vignettes = TRUE)

Quick start

The bundled simulation contains 1,000 cells and 500 genes. For a quick example, the code below uses 20 differentially expressed genes, 40 null genes, and 100 permutations. Increase n_perm to at least 1,000 for an analysis intended for inference and examine stability across random seeds.

library(scFPCDE)

data(scFPCDE_simdata)
gene_index <- c(1:20, 101:140)
cell_index <- seq(1, length(scFPCDE_simdata$tt), length.out = 200)
cell_index <- unique(round(cell_index))

yt <- scFPCDE_simdata$yt[cell_index, gene_index]
tt <- scFPCDE_simdata$tt[cell_index]

set.seed(2026)
res <- scFPCDE_run(
  yt = yt,
  tt = tt,
  n_perm = 100,
  ncores = 1
)

head(res$D_test_result)
scores_for_plot <- scFPCDE_fpc_scores(
  res,
  components = 1:2,
  transform = "signed_log10"
)
hist(
  res$D_test_result$p_value,
  breaks = 20,
  main = "D-test permutation p-values",
  xlab = "p-value"
)

scFPCDE_gene_curves(
  tt = tt,
  yt = scale(yt, center = TRUE, scale = FALSE),
  yt_fit = res$fpca_result$xt_hat,
  cell_cluster = scFPCDE_simdata$clusters[cell_index],
  subset = order(res$D_test_result$D_obs, decreasing = TRUE)[1:12],
  point_size = 0.45,
  point_alpha = 0.55,
  curve_linewidth = 0.9
)

scFPCDE_run() returns three named components:

• fpca_result: the fitted FPCA model and trajectories;
• D_test_result: gene-level D statistics, p-values, and BH-adjusted q-values;
• F_test_result: gene-level F-test results when use_FPC_F = TRUE, otherwise NULL.

Use scFPCDE_fpc_scores() to extract raw gene-level FPC scores or create signed-log10-compressed and standardized coordinates for visualization. Keep the raw scores for inference, distance calculations, and null boundaries.

See vignette("scFPCDE-overview") for a guided workflow and the function help pages for parameter details.

Citation

Run citation("scFPCDE") to obtain the package citation. Publication metadata can be added when the associated manuscript citation is final.

License

This package is released under the MIT License.