select-columns

Overview

kgtk select-columns selects a subsetfile columns while copying a KGTK file from input to output. You provide a list of column names in the order in which they should appear in the output file. This command is equivalent to kgtk reorder-columns --trim.

For more details, see kgtk reorder-columns --trim.

Usage

usage: kgtk reorder-columns [-h] [-i INPUT_FILE] [-o OUTPUT_FILE] -c
                            COLUMN_NAME [COLUMN_NAME ...]
                            [--as COLUMN_NAME [COLUMN_NAME ...]]
                            [--trim [True|False]] [-v [optional True|False]]

This command reorders one or more columns in a KGTK file. 

Reorder all columns using --columns col1 col2
Reorder selected columns using --columns col1 col2 ... coln-1 coln
Move a column to the front: --columns col ...
Move a column to the end: --columns ... col
Extract named columns, omitting the rest: --columns col1 col2 --trim
Move a range of columns: --columns coln .. colm ...
If no input filename is provided, the default is to read standard input. 

Additional options are shown in expert help.
kgtk --expert reorder-columns --help

optional arguments:
  -h, --help            show this help message and exit
  -i INPUT_FILE, --input-file INPUT_FILE
                        The KGTK input file. (May be omitted or '-' for
                        stdin.)
  -o OUTPUT_FILE, --output-file OUTPUT_FILE
                        The KGTK output file. (May be omitted or '-' for
                        stdout.)
  -c COLUMN_NAME [COLUMN_NAME ...], --columns COLUMN_NAME [COLUMN_NAME ...], --column COLUMN_NAME [COLUMN_NAME ...]
                        The list of reordered column names, optionally
                        containing '...' for column names not explicitly
                        mentioned.
  --as COLUMN_NAME [COLUMN_NAME ...], --as-columns COLUMN_NAME [COLUMN_NAME ...], --as-column COLUMN_NAME [COLUMN_NAME ...]
                        Replacement column names.
  --trim [True|False]   If true, omit unmentioned columns. (default=True).

  -v [optional True|False], --verbose [optional True|False]
                        Print additional progress messages (default=False).

Examples

Sample Data

Suppose that file1.tsv contains the following table in KGTK format:

kgtk cat -i examples/docs/reorder-columns-file1.tsv

node1	label	node2	location	years
john	zipcode	12345	home	10
john	zipcode	12346
peter	zipcode	12040	home
peter	zipcode	12040	cabin
peter	zipcode	12040	work	5
peter	zipcode	12040		6
steve	zipcode	45601		3
steve	zipcode	45601		4
steve	zipcode	45601		5
steve	zipcode	45601	home	1
steve	zipcode	45601	work	2
steve	zipcode	45601	cabin

Select a List of Column Names

Copy file1.tsv, sending the output to standard output, specifying the list of desired columnsL

kgtk select-columns -i examples/docs/reorder-columns-file1.tsv \
                    --columns label node1 node2

The result will be the following table in KGTK format:

label	node1	node2
zipcode	john	12345
zipcode	john	12346
zipcode	peter	12040
zipcode	peter	12040
zipcode	peter	12040
zipcode	peter	12040
zipcode	steve	45601
zipcode	steve	45601
zipcode	steve	45601
zipcode	steve	45601
zipcode	steve	45601
zipcode	steve	45601