Reading and writing in different formats

Heppy

Heppy histograms can be written to and read from the native text-based format using heppy.basehistogram.to_file() and heppy.from_file().

ROOT

Reading from a ROOT file:

heppy.readroot(rootfile, histpath, variation_paths={}, ignore_missing_variations=False, **kwargs)

Reads a histogram (possibly with systematic variations) from a ROOT file.

Parameters:

• rootfile (str) – path to ROOT file
• histopath (str) – path of the histogram inside the file
• variation_paths (dict of str : str) – optional dictionary of variation names (keys) and paths to the variation histograms inside the same ROOT file (values). NOTE: we can easily add the ability to read variation histograms also from other ROOT files than the nominal, get in touch if you want that.
• **kwargs –

  get passed on to histogram constructor. An important one is areas=False if retrieving ratios (e.g. efficiencies).

Converting to ROOT histograms and writing to ROOT files can be done using heppy.histogram1d.to_root() and heppy.histogram1d.to_root_file() (for 1D histograms) and heppy.histogram2d.to_root() and heppy.histogram2d.to_root_file() (for 2D histograms).

Rivet (YODA)

One-dimensional histograms can be written to the Rivet YODA format using heppy.histogram1d.to_yoda() or its synonym heppy.histogram1d.to_rivet().

TRExFitter (YAML)

Reading TRExFitter YAML format:

heppy.readtrex(trexfile, unfolded_format=False)

Reads Heppy histogram from TRExFitter YAML format.

Requires PyYAML.

IMPORTANT: the uncertainties are treated as correlated uncertainties, since their actual correlations cannot be inferred from the histogram. So treat them with care: they’re fine for plotting and looking at individual bins, but do not rebin the histogram or do statistical testing involving its shape and assume that you will find correct results.

Parameters:

• trexfile (str) – path to input file.
• unfolded_format (bool) – set this to True if reading the YAML format that TRExFitter uses for unfolded cross sections.

ATLAS Isolation and Fake Forum (XML)

Values with uncertainties can be converted to an XML string that the ATLAS Isolation and Fake Forum fake background tool understands in its configuration file using :py:func`heppy.Value.to_atlasiff`. You can use this for writing out e.g. fake factors.