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These keywords may be used, in addition to the
required keywords described in section 3.4.1
, to describe the structure of ASCII table data. They are not required,
but if they are used in an ASCII table header, they must be used as described
here. These keywords should not be used in other extensions unless they have
a function analogous to the one they have in the ASCII table extension. They
may appear anywhere between the TFIELDS and END keywords,
in any order.
- TTYPEn (character) is the heading for field n. The
recommended characters are letters, digits, and underscore. Upper case
values are preferred, but lowercase
letters may be used, and string comparisons involving the values
of TTYPEn keywords should not be case sensitive. The hyphen
is permitted but not recommended. While more
than one field may have the same heading (value of TTYPEn), the
practice is not recommended.
- TUNITn (character) is the physical units of field
n. The rules governing the units to be used in ASCII tables
are the same as those for a primary data array, as given in section 3.1.1.4.
- TSCALn (floating) is the scale factor for field
n, as applied in equation 3.11.
The default value is 1.0.
- TZEROn (floating) is the offset for field n
(see equation 3.11). The default value is 0.0.
Physical_value = (Stored_value)
× TSCALn + TZEROn. |
(3.11) |
Note: TSCALn and TZEROn may not be
used for A-format fields.
- TNULLn (character) is the representation of an undefined
value. The string chosen does not have to be readable in the
format specified by TFORMn; for example, a null value of
'***' might be used for an I3 field. If the null string given as
the value of the keyword does not fill the field, it is assumed to begin
at the start of the field, and the part of the field following the
string is assumed to be filled with blanks. A table will be more
efficiently read if TNULLn is specified only when null values
actually exist in the field, thus avoiding unnecessary string
comparisons for the other fields.
Next: Data Records in an
Up: ASCII Table Extension
Previous: Required Keywords for ASCII