Unit Contrast

Construct a contrast that sums to 1 and is used to define contrasts against the baseline.

Usage

unit_contrast(A, name, where = NULL)

Arguments

A

A formula selecting the cells to average. A logical expression (e.g. ~ cond == "A") selects the matching cells; a bare factor name (e.g. ~ cond) selects every cell. For a multi-basis HRF the weights are repeated on every basis function of the selected cells.

name

A character string specifying the name of the contrast.

where

An optional formula specifying the subset of conditions to apply the contrast to.

Value

A unit_contrast_spec object containing the contrast that sums to 1.

Examples

# Test main effect of Face against baseline
con <- unit_contrast(~ Face, name="Main_face")

# Test main effect within specific blocks
con2 <- unit_contrast(~ Face, name="Face_early", where = ~ block <= 3)