Skip to contents

Convert statistical result FBMs to FreeSurfer `.mgh` format

Source: R/vw_postprocess.R
convert_to_mgh.Rd

This function takes a list of FBM objects storing statistical results and writes them to FreeSurfer-compatible `.mgh` files. It supports coefficient, standard error, p-value, and residual maps, with optional on-the-fly \(-\log_{10}\) transformation of p-values.

Usage

convert_to_mgh(
  vw_results,
  result_path,
  stacks,
  stat_names = c("coef", "se", "p", "-log10p", "resid"),
  verbose = TRUE
)

Arguments

vw_results

A named list of FBM objects containing the statistical results.

result_path

Character string indicating the base output path where the .mgh files will be written.

stacks

Vector of stack identifiers (e.g. hemisphere stack IDs) to be included in output filenames (for non-residual stats).

stat_names

Character vector of statistic names to process. Default: c("coef","se","p","-log10p","resid"). The special name "-log10p" triggers the on-the-fly p-value transformation.

verbose

Logical. Default: TRUE

Value

Invisibly returns NULL. Side effects: .mgh files are written to disk.

Details

For residuals, all rows are written into a single .mgh file. For other stats, data is written to one file per row (i.e. term).

When computing \(-\log_{10}(p)\) values, the transformation is applied **in chunks of columns** to avoid loading the full FBM into memory.

Examples

if (FALSE) { # \dontrun{
library(bigstatsr)

# Dummy vw_results list with small FBMs
vw_results <- list(
  coef = FBM(5, 10, init = rnorm(50)),
  se   = FBM(5, 10, init = runif(50, 0.1, 1)),
  p    = FBM(5, 10, init = runif(50, 0, 1)),
  resid= FBM(20, 10, init = rnorm(200))
)

convert_to_mgh(
  vw_results = vw_results,
  result_path = "my_results/stat",
  stacks = 1:5
)
} # }