Reorder columns¶

The reorder_columns operation reorders the indicated columns in the specified order. This operation is often used to place the most important columns near the beginning of the file for readability or to assure that all the data files in dataset have the same column order. Additional parameters control how non-specified columns are treated.

Purpose¶

Use this operation to:

Ensure consistent column order across dataset files
Place important columns at the beginning for readability
Conform to standards (e.g., BIDS requires onset and duration first)
Remove unwanted columns while reordering (using keep_others=false)

Parameters¶

Parameters for the reorder_columns operation.

Parameter	Type	Description
column_order	list	A list of columns in the order they should appear in the data.
ignore_missing	bool	Controls handling column names in the reorder list that aren’t in the data.
keep_others	bool	Controls handling of columns not in the reorder list.

If ignore_missing is true and items in the reorder list do not exist in the file, the missing columns are ignored. On the other hand, if ignore_missing is false, a column name in the reorder list that is missing from the data raises a ValueError.

The keep_others parameter controls whether columns in the data that do not appear in the column_order list are dropped (keep_others is false) or put at the end in the relative order that they appear in the file (keep_others is true).

BIDS event files are required to have onset and duration as the first and second columns, respectively.

Example¶

The reorder_columns operation in the following example specifies that the first four columns of the dataset should be: onset, duration, response_time, and trial_type. Since keep_others is false, these will be the only columns retained.

A JSON file with a single reorder_columns transformation operation.

[{   
    "operation": "reorder_columns",
    "description": "Reorder columns.",
    "parameters": {
        "column_order": ["onset", "duration", "response_time",  "trial_type"],
        "ignore_missing": true,
        "keep_others": false
    }
}]

Results¶

The results of executing the previous reorder_columns transformation on the sample remodel event file are:

Results of reorder_columns.

onset	duration	response_time	trial_type
0.0776	0.5083	0.565	go
5.5774	0.5083	0.49	unsuccesful_stop
9.5856	0.5084	0.45	go
13.5939	0.5083	n/a	succesful_stop
17.1021	0.5083	0.633	unsuccesful_stop
21.6103	0.5083	0.443	go

Notes¶

With keep_others=false, this operation can also remove columns
BIDS standard requires onset and duration as the first two columns
Set ignore_missing=true for robust operation across varied datasets
Unspecified columns are appended at the end if keep_others=true
Useful for ensuring consistency across multiple event files in a dataset
Can be combined with other operations for complete dataset reorganization