MATLAB Function Reference

fitsinfo - Information about FITS file

Syntax

info = fitsinfo(filename)

Description

info = fitsinfo(filename) returns the structure, info, with fields that contain information about the contents of a Flexible Image Transport System (FITS) file. filename is a string enclosed in single quotes that specifies the name of the FITS file.

The info structure contains the following fields, listed in the order they appear in the structure. In addition, the info structure can also contain information about any number of optional file components, called extensions in FITS terminology. For more information, see FITS File Extensions.

Field Name	Description	Return Type
`Filename`	Name of the file	String
`FileModDate`	File modification date	String
`FileSize`	Size of the file in bytes	Double
`Contents`	List of extensions in the file in the order that they occur	Cell array of strings
`PrimaryData`	Information about the primary data in the FITS file	Structure array

PrimaryData

The PrimaryData field is a structure that describes the primary data in the file. The following table lists the fields in the order they appear in the structure.

Field Name	Description	Return Type
`DataType`	Precision of the data	String
`Size`	Array containing the size of each dimension	Double array
`DataSize`	Size of the primary data in bytes	Double
`MissingDataValue`	Value used to represent undefined data	Double
`Intercept`	Value, used with `Slope`, to calculate actual pixel values from the array pixel values, using the equation: `actual_value = Slope*array_value + Intercept`	Double
`Slope`	Value, used with `Intercept`, to calculate actual pixel values from the array pixel values, using the equation: `actual_value = Slope*array_value + Intercept`	Double
`Offset`	Number of bytes from beginning of the file to the location of the first data value	Double
`Keywords`	A number-of-keywords-by-3 cell array containing keywords, values, and comments of the header in each column	Cell array of strings

FITS File Extensions

A FITS file can also include optional extensions. If the file contains any of these extensions, the info structure can contain these additional fields.

AsciiTable — Numeric information in tabular format, stored as ASCII characters
BinaryTable — Numeric information in tabular format, stored in binary representation
Image — A multidimensional array of pixels
Unknown — Nonstandard extension

AsciiTable Extension

The AsciiTable structure contains the following fields, listed in the order they appear in the structure.

Field Name	Description	Return Type
`Rows`	Number of rows in the table	Double
`RowSize`	Number of characters in each row	Double
`NFields`	Number of fields in each row	Double array
`FieldFormat`	A 1-by-`NFields` cell containing formats in which each field is encoded. The formats are FORTRAN-77 format codes.	Cell array of strings
`FieldPrecision`	A 1-by-`NFields` cell containing precision of the data in each field	Cell array of strings
`FieldWidth`	A 1-by-`NFields` array containing the number of characters in each field	Double array
`FieldPos`	A 1-by-`NFields` array of numbers representing the starting column for each field	Double array
`DataSize`	Size of the data in the table in bytes	Double
`MissingDataValue`	A 1-by-`NFields` array of numbers used to represent undefined data in each field	Cell array of strings
`Intercept`	A 1-by-`NFields` array of numbers used along with `Slope` to calculate actual data values from the array data values using the equation: `actual_value = Slope*array_value+Intercept`	Double array
`Slope`	A 1-by-`NFields` array of numbers used with `Intercept` to calculate true data values from the array data values using the equation: `actual_value = Slope*array_value+Intercept`	Double array
`Offset`	Number of bytes from beginning of the file to the location of the first data value in the table	Double
`Keywords`	A number-of-keywords-by-3 cell array containing all the Keywords, Values and Comments in the ASCII table header	Cell array of strings

BinaryTable Extension

The BinaryTable structure contains the following fields, listed in the order they appear in the structure.

Field Name	Description	Return Type
`Rows`	Number of rows in the table	Double
`RowSize`	Number of bytes in each row	Double
`NFields`	Number of fields in each row	Double
`FieldFormat`	A 1-by-`NFields` cell array containing the data type of the data in each field. The data type is represented by a FITS binary table format code.	Cell array of strings
`FieldPrecision`	A 1-by-`NFields` cell containing precision of the data in each field	Cell array of strings
`FieldSize`	A 1-by-`NFields` array, where each element contains the number of values in the Nth field	Double array
`DataSize`	Size of the data in the Binary Table, in bytes. Includes any data past the main table.	Double
`MissingDataValue`	An 1-by-`NFields` array of numbers used to represent undefined data in each field	Cell array of double
`Intercept`	A 1-by-`NFields` array of numbers used along with Slope to calculate actual data values from the array data values using the equation: `actual_value = slope*array_value+Intercept`	Double array
`Slope`	A 1-by-`NFields` array of numbers used with Intercept to calculate true data values from the array data values using the equation: `actual_value = Slope*array_value+Intercept`	Double array
`Offset`	Number of bytes from beginning of the file to the location of the first data value	Double
`ExtensionSize`	Size of any data past the main table, in bytes	Double
`ExtensionOffset`	Number of bytes from the beginning of the file to any data past the main table	Double
`Keywords`	A number-of-keywords-by-3 cell array containing all the Keywords, values, and comments in the Binary Table header	Cell array of strings

Image Extension

The Image structure contains the following fields, listed in the order they appear in the structure.

Field Name	Description	Return Type
`DataType`	Precision of the data	String
`Size`	Array containing sizes of each dimension	Double array
`DataSize`	Size of the data in the Image extension in bytes	Double
`Offset`	Number of bytes from the beginning of the file to the first data value	Double
`MissingDataValue`	Value used to represent undefined data	Double
`Intercept`	Value, used with `Slope`, to calculate actual pixel values from the array pixel values, using the equation: `actual_value = Slope*array_value+Intercept`	Double
`Slope`	Value, used with `Intercept`, to calculate actual pixel values from the array pixel values, using the equation: `actual_value = Slope*array_value + Intercept`	Double
`Keywords`	A number-of-keywords-by-3 cell array containing all the Keywords, values, and comments in the Binary Table header	Cell array of strings

Unknown Structure

The Unknown structure contains the following fields, listed in the order they appear in the structure.

Field Name	Description	Return Type
`DataType`	Precision of the data	String
`Size`	Sizes of each dimension	Double array
`DataSize`	Size of the data in nonstandard extensions, in bytes	Double
`Offset`	Number of bytes from beginning of the file to the first data value	Double
`MissingDataValue`	Representation of undefined data	Double
`Intercept`	Value, used with `Slope`, to calculate actual data values from the array data values, using the equation: `actual_value = Slope*array_value+Intercept`	Double
`Slope`	Value, used with `Intercept`, to calculate actual data values from the array data values, using the equation: `actual_value = Slope*array_value+Intercept`	Double
`Keywords`	A number-of-keywords-by-3 cell array containing all the Keywords, values, and comments in the Binary Table header	Cell array of strings

Example

Use fitsinfo to obtain information about the FITS file tst0012.fits. In addition to its primary data, the file also contains an example of the extensions BinaryTable, Unknown, Image, and AsciiTable.

S = fitsinfo('tst0012.fits');
S = 
         Filename: [1x71 char]
      FileModDate: '12-Mar-2001 18:37:46'
         FileSize: 109440
         Contents: {'Primary' 'Binary Table' 'Unknown' 
'Image' 'ASCII Table'}
      PrimaryData: [1x1 struct]
      BinaryTable: [1x1 struct]
          Unknown: [1x1 struct]
            Image: [1x1 struct]
       AsciiTable: [1x1 struct]

The PrimaryData field describes the data in the file. For example, the Size field indicates the data is a 102-by-109 matrix.

S.PrimaryData
         DataType: 'single'
             Size: [102 109]
         DataSize: 44472
 MissingDataValue: []
        Intercept: 0
            Slope: 1
           Offset: 2880
         Keywords: {25x3 cell}

The AsciiTable field describes the AsciiTable extension. For example, using the FieldWidth and FieldPos fields you can determine the length and location of each field within a row.

S.AsciiTable
ans = 
             Rows: 53
          RowSize: 59
          NFields: 8
      FieldFormat: {'A9' 'F6.2' 'I3' 'E10.4' 'D20.15' 'A5' 'A1' 'I4'}
   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}