Next Previous Up Contents
Next: GBIN
Up: Supported Input Formats
Previous: IPAC

4.1.1.9 Comma-Separated Values

Comma-separated value ("CSV") format is a common semi-standard text-based format in which fields are delimited by commas. Spreadsheets and databases are often able to export data in some variant of it. The intention is that TOPCAT can read tables in the version of the format spoken by MS Excel amongst other applications, though the documentation on which it was based was not obtained directly from Microsoft.

The rules for data which it understands are as follows:

Note that you can not use a "#" character (or anything else) to introduce "comment" lines.

Because the CSV format contains no metadata beyond column names, TOPCAT is forced to guess the datatype of the values in each column. It does this by reading the whole file through once and guessing on the basis of what it has seen. This has the disadvantages:

This means that CSV is not generally recommended if you can use another format instead. If you're stuck with a large CSV file that's misbehaving or slow to use, one possibility is to turn it into an ECSV file by adding some header lines by hand.

This format is not detected automatically - you must specify that you wish to load a table in csv format.


Next Previous Up Contents
Next: GBIN
Up: Supported Input Formats
Previous: IPAC

TOPCAT - Tool for OPerations on Catalogues And Tables
Starlink User Note253
TOPCAT web page: http://www.starlink.ac.uk/topcat/
Author email: m.b.taylor@bristol.ac.uk
Mailing list: topcat-user@jiscmail.ac.uk