# Planning Simulations to use LightCones or LightRays¶

If you want to run a cosmological simulation that will have just enough data outputs to create a light cone or light ray, the plan_cosmology_splice() function will calculate a list of redshifts outputs that will minimally connect a redshift interval.

from yt.analysis_modules.cosmological_observation.api import CosmologySplice
my_splice = CosmologySplice('enzo_tiny_cosmology/32Mpc_32.enzo', 'Enzo')
my_splice.plan_cosmology_splice(0.0, 0.1, filename='redshifts.out')


This will write out a file, formatted for simulation type, with a list of redshift dumps. The keyword arguments are:

• decimals (int): The decimal place to which the output redshift will be rounded. If the decimal place in question is nonzero, the redshift will be rounded up to ensure continuity of the splice. Default: 3.
• filename (str): If provided, a file will be written with the redshift outputs in the form in which they should be given in the enzo parameter file. Default: None.
• start_index (int): The index of the first redshift output. Default: 0.