fitsread

Read data from FITS file

Syntax

data = fitsread(filename)

data = fitsread(filename,'raw')

data = fitsread(filename,extname)

data = fitsread(filename,extname,index)

data = fitsread(filename,...,Name,Value)

Description

data = fitsread(filename) reads the primary data of the Flexible Image Transport System (FITS) file specified by filename and returns it as an adjusted array. The function replaces undefined data values with NaN and scales numeric data by the slope and intercept values, always returning double precision values .

data = fitsread(filename,'raw') reads the primary data of the FITS file without adjustment. This syntax does not scale the data read from the file, replace undefined values with NaN. The returned data maintains the class type specified in the file.

data = fitsread(filename,extname) reads data from the FITS file extension specified by extname. The FITS file contains primary data and can optionally contain any number of optional components, called extensions in FITS terminology.

data = fitsread(filename,extname,index) also specifies the index when several of the same extension type exist.

data = fitsread(filename,...,Name,Value) reads data from the FITS file with additional options using one or more Name-Value arguments. For example, TableColumns specifies which columns to read.

Examples

Read FITS File

Read primary data from a FITS file.

data = fitsread('tst0012.fits');

Examine the output variable data.

whos data

  Name        Size             Bytes  Class     Attributes

  data      109x102            88944  double              

Read Raw Data From FITS File

Read primary data from a FITS file as raw data.

data = fitsread('tst0012.fits', 'raw');

Examine the output variable data.

whos data

  Name        Size             Bytes  Class     Attributes

  data      109x102            44472  single              

Read FITS File With Image Extension

Explore the extensions of a FITS file and read data from the image extension.

List the contents of a FITS file, including any extensions if present.

info = fitsinfo('tst0012.fits');
disp(info.Contents);

  Columns 1 through 4

    {'Primary'}    {'Binary Table'}    {'Unknown'}    {'Image'}

  Column 5

    {'ASCII Table'}

Read data from the image extension of the FITS file.

imageData = fitsread('tst0012.fits','image');

Read Subsample of FITS File

Read a subsample of data from a FITS file.

First, get information about the FITS file.

info = fitsinfo('tst0012.fits')

info = struct with fields:
       Filename: '/mathworks/devel/bat/Bdoc21a/build/matlab/toolbox/matlab/demos/tst0012.fits'
    FileModDate: '12-Mar-2001 18:37:46'
       FileSize: 109440
       Contents: {1x5 cell}
    PrimaryData: [1x1 struct]
    BinaryTable: [1x1 struct]
        Unknown: [1x1 struct]
          Image: [1x1 struct]
     AsciiTable: [1x1 struct]

Query the sizes of each dimension of the image extension.

info.Image.Size

ans = 1×3

    31    73     5

Store the row and column sizes.

rowend = info.Image.Size(1);
colend = info.Image.Size(2);

Read every other row and column from the fifth element of the third dimension of the FITS file.

 primaryData = fitsread('tst0012.fits','image', ...
              'Info', info,...
              'PixelRegion',{[1 2 rowend], [1 2 colend], 5 });

Read Specified Rows From FITS File ASCII Table

Read every other row from the ASCII table of a FITS file.

Determine the number of rows in the ASCII table.

info = fitsinfo('tst0012.fits');
rowend = info.AsciiTable.Rows;

Read every other row from the ASCII table.

tableData = fitsread('tst0012.fits','asciitable',...
                    'Info',info,...
                    'TableRows',[1:2:rowend]);

Read Specified Columns of a FITS File Binary Table

Read all data for the first, second, and fifth columns of the binary table of a FITS file.

Determine the number of rows in the binary table.

info      = fitsinfo('tst0012.fits');
rowend    = info.BinaryTable.Rows;

Read first, second, and fifth columns of the binary table.

tableData = fitsread('tst0012.fits','binarytable', ...
                    'Info',info,...
                    'TableColumns',[1 2 5]);

Input Arguments

filename — File name

character vector | string scalar

File name, specified as a character vector or string scalar.

extname — Data array or extension name

'primary' | 'asciitable' | 'binarytable' | 'image' | 'unknown'

Data array or extension name, specified as a character vector or a string scalar. The FITS file contains primary data and can optionally contain any number of optional components, called extensions in FITS terminology. To determine the contents of the FITS file, view the Contents field of the structure returned by fitsinfo.

Extname	Description
'primary'	Read data from the primary data array.
'asciitable'	Read data from the ASCII table extension as a one-dimensional cell array.
'binarytable'	Read data from the binary table extension as a one-dimensional cell array.
'image'	Read data from the image extension.
'unknown'	Read data from the unknown extension.

index — Index

scalar

Index, specified as a scalar indicating which extension to read if multiple extensions of the same type exist.

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is the argument name and Value is the corresponding value. Name must appear inside quotes. You can specify several name and value pair arguments in any order as Name1,Value1,...,NameN,ValueN.

'Info' — Information

structure array

Information, specified as the structure array specifying the location of the data to read. The information structure array can be obtained through fitsinfo. Specifying Info can significantly improve performance, especially when reading multiple images from the file.

'PixelRegion' — Pixel region

cell array

Pixel region, specified as a cell array of vectors. Each vector corresponds to a dimension of the data. To specify a subregion to read from the Nth dimension, use the Nth vector in the cell array. Each vector in the cell array must be formatted as one of the following.

Vector Format	Description
start	Start point within the dimension. The default stop point is the end of the dimension.
[start stop]	Start and stop points within the dimension.
[start increment stop]	Start and stop points of the dimension and the increment by which to read.

The pixel region parameter is valid only for the primary or image extensions.

'TableColumns' — Columns to read

one-dimensional array

Columns to read, specified as a one-dimensional array containing the indices of columns to read from the ASCII or binary table extension. The vector must contain unique and valid indices into the table data specified in increasing order. This parameter is valid only for the ASCII or binary extensions.

'TableRows' — Rows to read

one-dimensional array

Rows to read, specified as a one-dimensional array containing the indices of rows to read from the ASCII or binary table extension. The vector must contain unique and valid indices into the table data specified in increasing order. This parameter is valid only for the ASCII or binary extensions.

References

For copyright information, see the cfitsiocopyright.txt file. View this file using the open function.

open cfitsiocopyright.txt