matlab.io.fits.readKeyUnit

Read physical units string from keyword

Syntax

units = matlab.io.fits.readKeyUnit(fptr,keyname)

Description

units = matlab.io.fits.readKeyUnit(fptr,keyname) returns the physical units from the specified keyword. Specify the keyname argument as a string scalar or character vector. The function returns units as a character vector. If no units are defined, the function returns units as an empty character vector.

Examples

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Read Units of Key Value

Open Live Script

Create a new FITS file and add an image and a key with units to it.

import matlab.io.*
fptr = fits.createFile("myfile.fits");
fits.createImg(fptr,"long_img",[10 20])
fits.writeKey(fptr,"VELOCITY",12.3,"orbital speed")
fits.writeKeyUnit(fptr,"VELOCITY","km/s")

Read the units for the key value and then delete the file.

units = fits.readKeyUnit(fptr,"VELOCITY")

units = 
'km/s'

fits.closeFile(fptr)
delete myfile.fits

Tips

This function corresponds to the fits_read_key_unit (ffgunt) function in the CFITSIO library C API.
To use this function, you must be familiar with the CFITSIO C interface. You can access the CFITSIO documentation at the CFITSIO website.

Extended Capabilities

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Thread-Based Environment
Run code in the background using MATLAB® `backgroundPool` or accelerate code with Parallel Computing Toolbox™ `ThreadPool`. (since R2026a)

The matlab.io.fits.readKeyUnit function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

Version History