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SECTION 6. RANDOM GROUPS STRUCTURE

6.2

Data Sequence

Random groups data shall consist of a set of groups. The number of groups shall be

specified by the GCOUNT keyword in the associated header. Each group shall consist of

the number of parameters specified by the PCOUNT keyword followed by an array with

the number of elements Nelem given by the following expression:

Nelem  = (NAXIS2 × NAXIS3 × · · · × NAXISm),

(6.3)

where Nelem is the number of elements in the data array in a group, m is the value of

NAXIS, and the NAXISn represent the values associated with those keywords.

The first parameter of the first group shall appear in the first location of the first

data block. The first element of each array shall immediately follow the last parameter

associated with that group. The first parameter of any subsequent group shall imme-

diately follow the last element of the array of the previous group. The arrays shall be

organized internally in the same way as an ordinary primary data array. If the groups

data do not fill the final data block, the remainder of the block shall be filled with zero

values in the same way as a primary data array (§3.3.2). If random groups records are

present, there shall be no primary data array.

6.3

Data Representation

Permissible data representations are those listed in §5. Parameters and elements of

associated data arrays shall have the same representation. If more precision is required

for an associated parameter than for an element of a data array, the parameter shall

be divided into two or more addends, represented by the same value for the PTYPEn

keyword. The value shall be the sum of the physical values, which may have been

obtained from the group parameter values using the PSCALn and PZEROn keywords.

FITS Standard