Snakebids is configured with a YAML (or JSON) file that extends the standard snakemake config file with variables that snakebids uses to parse an input BIDS dataset and expose the snakebids workflow to the command line.

Config Variables

pybids_inputs: A dictionary that describes each type of input you want to grab from an input BIDS dataset. The value of each item should be a dictionary with keys filters and wildcards. The value of filters should be a dictionary where each key corresponds to a BIDS entity, and the value specifies which values of that entity should be grabbed. The value of wildcards should be a list of BIDS entities that should be present, but specifies that all values of that entity should be grabbed. The dictionary for each input is passed directly to PyBIDS’ get() function.

In the following (YAML-formatted) example, the bold input type is specified. BIDS files with the datatype func, suffix bold, and extension .nii.gz will be grabbed, and the subject, session, acquisition, task, and run entities of those files will be left as wildcards.

    suffix: 'bold'
    extension: '.nii.gz'
    datatype: 'func'
    - subject
    - session
    - acquisition
    - task
    - run

analysis_levels: A list of analysis levels in the BIDS app. Typically, this will include participant and/or group. Note that the default (YAML) configuration file expects this mapping to be identified with the anchor analysis_levels to be aliased by parse_args.

targets_by_analysis_level: A mapping from the name of each analysis_level to the list of rules or files to be run for that analysis level.

parse_args: A dictionary of command-line parameters to make available as part of the BIDS app. Each item of the mapping is passed to argparse’s add_argument function. A number of default entries are present in a new snakebids project’s config file that structure the BIDS app’s CLI, but additional command-line arguments can be added as necessary.

debug: A boolean that determines whether debug statements are printed during parsing. Should be disabled (False) if you’re generating DAG visualization with snakemake.

derivatives: A boolean (or path(s) to derivatives datasets) that determines whether snakebids will search in the derivatives subdirectory of the input dataset.