esheldon
Comments for binary table columns
Dear all,
I create fits file with the following (simplified) script:
import fitsio, numpy
from fitsio import FITS,FITSHDR
filename='test.fits'
fits = FITS(filename,'rw')
data = numpy.zeros(1, dtype=[('freq','i4')])
data[0]['freq'] = 0
hdr = [
{'name':'TSTART', 'value': 0, 'comment':'Moment when this log file was started'},
]
fits.write(data, units=["Hz"], extname="logs", header=hdr)
fits.close()
File is created correctly with units being assigned as units for the column "freq" but when I check the header, e.g. with
data,h = fitsio.read(filename, header=True)
I see the following:
XTENSION= 'BINTABLE' / binary table extension BITPIX = 8 / 8-bit bytes NAXIS = 2 / 2-dimensional binary table NAXIS1 = 4 / width of table in bytes NAXIS2 = 1 / number of rows in table PCOUNT = 0 / size of special data area GCOUNT = 1 / one data group (required keyword) TFIELDS = 1 / number of fields in each row TTYPE1 = 'freq ' / label for field 1 TFORM1 = 'J ' / data format of field: 4-byte INTEGER TUNIT1 = 'Hz ' / physical unit of field EXTNAME = 'logs ' / name of this binary table extension TSTART = 0 / Moment when this log file was started
Can I somehow change the "label for field 1" comment for the TTYPE1 to put a description of the physical meaning of the data in the "freq" column?
Thank you for any help.
P.S. I tried to create file in such a way, then read the data and header, modify the header by inserting custom comment in h._record_map and execute with modified header (h_new) the fits.write(...) again, like this:
fits.write(data, units=["Hz"], extname="logs", header=h_new)
But as a result I get exactly the same headers, so probably the create_table_hdu(...) overwrites the header with identical to original one with empty comment which is then replaced with the standard "label for field 1" string.
I'm sorry I didn't reply to this earlier. I think this should be possible, but would be some work to implement. Is this something you would like to contribute?
