Astro::STSDAS::Table::Column - An object representing column information
An Astro::STSDAS::Table::Column object represents a single column in an STSDAS table. It does not store data for the column; it simply manages attributes of the column. The following attributes exist for all columns:
the column name
the column units
the column format
the index of the column in the table (unary based)
Binary table columns have the following additional attributes:
the byte offset from the start of the row (for row ordered tables)
the data representation type. See Astro::STSDAS::Table::Constants.
the number of items in a column element. If the data type is a string, this is the maximum number of characters. if not a string, and if greater than one, it indicates a vector.
A Perl pack() compatible format used to parse this column. This takes into account the number of elements in a vector.
The number of bytes in the data type
A Perl pack() compatible format used to parse this column. This does not take into account the number of elements in a vector.
Each attribute has an eponymously named method with which the attribute value may be retrieved. The method may also be used to set attributes' values for modifiable attributes. For example:
$oldname = $col->name; $col->name( $newname );
Modifiable attributes are:
format. If a set of columns is being managed in an Astro::STSDAS::Table::Columns container, it is very important to use that container's rename method to change a column's name, else the container will get very confused.
$column = Astro::STSDAS::Table::Column->new( $name, $units, $format, $idx, $offset, $type, $nelem );
This is the constructor. It returns an Astro::STSDAS::Table::Column object. Attributes which are inappropriate for the column may be passed as undef. See above for the definition of the attributes. This is generally only called by a Astro::STSDAS::Table::Columns object.
This returns true if the column is a string column.
$bad_value = $col->is_indef( $value );
This determines if the passed value matches the undefined value appropriate to the column.
Returns true if the column's elements are vectors.
This returns the number of items in a column element. This will normally be
1, except for vector columns.
This returns a copy of the column (as an Astro::STSDAS::Table::Column object).
None by default.
This software is released under the GNU General Public License. You may find a copy at
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