MATLAB Function Reference |
Return information about FITS file
Syntax
Description
S = fitsinfo(filename)
returns a structure whose fields contain information about the contents of a Flexible Image Transport System (FITS) file. filename
is a string that specifies the name of the FITS file.
The structure S
contains the following fields.
Field Name |
Description |
Return Type |
Contents |
List of extensions in the file in the order that they occur |
Cell array of strings |
FileModDate |
File modification date |
String |
Filename |
Name of the file |
String |
FileSize |
Size of the file in bytes |
Double |
PrimaryData |
Information about the primary data in the FITS file |
Structure array |
A FITS file can also include any number of optional components, called extensions, in FITS terminology. To provide information about these extensions, the structure S
can also include one or more of the following structure arrays.
Field Name |
Description |
Return Type |
AsciiTable |
ASCII Table extensions |
Structure array |
BinaryTable |
Binary Table extensions |
Structure array |
Image |
Image extensions |
Structure array |
Unknown |
Nonstandard extensions |
Structure array |
The tables that follow show the fields of each of the structure arrays that can be returned by fitsinfo
.
Note
For all Intercept and Slope field names below, the equation used to calculate actual values is actual_value = (Slope * array_value) + Intercept .
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Example
Use fitsinfo
to obtain information about FITS file tst0012.fits
. In addition to its primary data, the file also contains three extensions: Binary Table, Image, and ASCII Table.
S = fitsinfo('tst0012.fits'); S = Filename: 'tst0012.fits' FileModDate: '27-Nov-2000 13:25:55' FileSize: 109440 Contents: {'Primary' 'Binary Table' 'Image' 'ASCII'} PrimaryData: [1x1 struct] BinaryTable: [1x1 struct] Image: [1x1 struct] AsciiTable: [1x1 struct]
The PrimaryData
substructure shows that the data resides in a 102-by-109 matrix of single-precision values. There are 44,472 bytes of primary data starting at an offset of 2,880 bytes from the start of the file.
S.PrimaryData ans = DataType: 'single' Size: [102 109] DataSize: 44472 MissingDataValue: [] Intercept: 0 Slope: 1 Offset: 2880 Keywords: {25x3 cell}
Examining the ASCII Table substructure, you can see that this table has 53 rows, 59 columns, and contains 8 fields per row. The last field in each row, for example, begins in the 55th column and contains a 4-digit integer.
S.AsciiTable ans = Rows: 53 RowSize: 59 NFields: 8 FieldFormat: {1x8 cell} FieldPrecision: {1x8 cell} FieldWidth: [9 6.2000 3 10.4000 20.1500 5 1 4] FieldPos: [1 11 18 22 33 54 54 55] DataSize: 3127 MissingDataValue: {'*' '---.--' '*' [] '*' '*' '*' ''} Intercept: [0 0 -70.2000 0 0 0 0 0] Slope: [1 1 2.1000 1 1 1 1 1] Offset: 103680 Keywords: {65x3 cell} S.AsciiTable.FieldFormat ans = 'A9' 'F6.2' 'I3' 'E10.4' 'D20.15' 'A5' 'A1' 'I4'
The ASCII Table includes 65 keyword entries arranged in a 65-by-3 cell array.
key = S.AsciiTable.Keywords key = S.AsciiTable.Keywords ans = 'XTENSION' 'TABLE' [1x48 char] 'BITPIX' [ 8] [1x48 char] 'NAXIS' [ 2] [1x48 char] 'NAXIS1' [ 59] [1x48 char] . . . . . . . . .
One of the entries in this cell array is shown here. Each row of the array contains a keyword, its value, and comment.
key{2,:} ans = BITPIX % Keyword ans = 8 % Keyword value ans = Character data 8 bits per pixel % Keyword comment
See Also
finish | fitsread |
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