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Heatmap visualization of the combined fmri_model design matrix

Source: R/fmri_model.R
design_map.fmri_model.Rd

Produces a single heatmap of all columns in the design matrix of an fmri_model, which merges the event_model and baseline_model regressors. Rows are scans (time runs downward); columns are regressors, kept in model order and grouped into panels by term (event terms, drift, intercept, nuisance). Run boundaries are marked with horizontal rules, and the subtitle reports the rank and condition number of the design.

By default each column is divided by its maximum absolute value, so regressors on very different scales (an intercept, a motion trace, a convolved event train) are all legible on one colour scale. Set scale_columns = FALSE to show raw values. Run-intercept columns are drawn in grey, since they carry no information beyond run membership.

The condition number is computed after scaling every column to unit length, so it reflects collinearity rather than the units of the columns.

Usage

# S3 method for class 'fmri_model'
design_map(
  x,
  block_separators = TRUE,
  rotate_x_text = TRUE,
  fill_midpoint = NULL,
  fill_limits = NULL,
  scale_columns = TRUE,
  ...
)

Arguments

x

An fmri_model object.

block_separators

Logical; if TRUE, draw rules between runs.

rotate_x_text

Logical; if TRUE, rotate x-axis labels to vertical.

fill_midpoint

Numeric or NULL; centre of the diverging colour scale. Defaults to 0.

fill_limits

Numeric vector of length 2 or NULL; passed to the fill scale limits= argument. This can clip or expand the color range.

scale_columns

Logical; if TRUE (default), scale each column to a maximum absolute value of 1.

...

Additional arguments passed to geom_raster.

Value

A ggplot2 plot object.