Prior calibration

If the prior parameters are not set manually by Setting the configuration, they can be estimated using a set of calibration data - unblended sources with photometric fluxes and known spectroscopic redshifts.

The blendz.Photoz.calibrate function just calls the prior-specific calibration function. As a result, if you define your own priors (see Specifying new priors), you will need to write your own calibration function.

The calibration function can be called by creating a Photoz object with configuration set to the calibration data. In this configuration, the prior_parameters option should be set to None.

pz_calib = blendz.Photoz(config_path='calibration_config.txt')
pz_calib.calibrate()

For the default priors, this will result in a file called calibrated_prior_config.txt being created. This is a configuration file with the prior parameters set to the maximum a posteriori parameters found in the calibration. This can then be read in alongside a photoz-configuration for sampling as normal.

pz = blendz.Photoz(config_path=['photoz_config.txt',
                                'calibrated_prior_config.txt'])

pz.sample([2, 1])

The photoz-configuration file should also have the prior_parameters option set to None.