pair_contrast: Pair Contrast

In bbuchsbaum/fmrireg: R package for the anlysis of fmri data

Pair Contrast

Description

Construct a sum-to-zero contrast between two logical expressions. This function is particularly useful for comparing specific conditions or combinations of conditions.

Usage

pair_contrast(A, B, name, where = NULL)

Arguments

A	A formula representing the first logical expression in the contrast.
B	A formula representing the second logical expression in the contrast.
name	A character string specifying the name of the contrast (mandatory).
where	An optional formula specifying the subset over which the contrast is computed.

Details

The contrast is constructed as (A - B), where A and B are logical expressions that evaluate to TRUE/FALSE for each observation. The resulting contrast weights sum to zero.

Value

A pair_contrast_spec object containing:

A	First logical expression
B	Second logical expression
where	Subsetting formula (if provided)
name	Contrast name

See Also

pairwise_contrasts for all pairwise comparisons, contrast_set for creating sets of contrasts

Examples

# Compare faces vs scenes
pair_contrast(~ category == "face", ~ category == "scene", name = "face_vs_scene")

# Compare with subsetting
pair_contrast(~ category == "face", ~ category == "scene",
             name = "face_vs_scene_block1",
             where = ~ block == 1)

bbuchsbaum/fmrireg documentation built on March 1, 2025, 11:20 a.m.