Loading Data

Below are instructions for loading all supported datasets.


The consistent-trees format is typically one or a few files with a naming convention like “tree_0_0_0.dat”. To load these files, just give the filename

import ytree
a = ytree.load("consistent_trees/tree_0_0_0.dat")

Rockstar Catalogs

Rockstar catalogs with the naming convention “out_*.list” will contain information on the descendent ID of each halo and can be loaded independently of consistent-trees. This can be useful when your simulation has very few halos, such as in a zoom-in simulation. To load in this format, simply provide the path to one of these files.

import ytree
a = ytree.load("rockstar/rockstar_halos/out_0.list")


Merger-trees created with TreeFarm (ytree’s merger-tree code for Gadget FoF/SUBFIND catalogs) can be loaded in by providing the path to one of the catalogs created during the calculation.

import ytree
a = ytree.load("tree_farm/tree_farm_descendents/fof_subhalo_tab_000.0.h5")

Saved Arbors

Once merger-tree data has been loaded, it can be saved to a universal format using save_arbor or save_tree. These can be loaded by providing the path to the primary hdf5 file.

import ytree
a = ytree.load("arbor/arbor.h5")

Saved Arbors from ytree 1.1

Arbors created with version 1.1 of ytree and earlier can be reloaded by providing the single file created. It is recommended that arbors be re-saved into the newer format as this will significantly improve performance.

import ytree
a = ytree.load("arbor.h5")