== [https://cds.cern.ch/record/1456844/files/CERN-OPEN-2012-016.pdf HistFactory] Input to calculate Combined SR exclusion limits ==

[https://cds.cern.ch/record/2684863/files/ATL-PHYS-PUB-2019-029.pdf HistFactory] JSON files can be attached to the analysis to be able to estimate exclusion limits of combined likelihood profiles and even global profile likelihoods. JSON files need to be under the same folder with info file and required information has to be added into the info file as shown below.

{{{
  <pyhf id="RegionA">
    <name>atlas_susy_2018_031_SRA.json</name>
    <regions>
      <channel name="SR_meff">
      SRA_L
      SRA_M
      SRA_H
      </channel>
      <channel name="VRtt_meff"></channel>
      <channel name="CRtt_meff"></channel>
    </regions>
  </pyhf>
}}}


where <pyhf id="RegionA"> is the identifier of the profile and will be printed in the output file to show the exclusion estimates calculated using this specific likelihood profile. It can be named as anything without using spaces. <name>atlas_susy_2018_031_SRA.json</name> is the name of the [https://cds.cern.ch/record/2684863/files/ATL-PHYS-PUB-2019-029.pdf HistFactory] JSON file. <channel name="SR_meff"> is the name of the channel as specified in the JSON file, please note that in case of the wrong declaration the profile will be ignored. In the example above, the channel ''SR_meff'' has 3 signal regions declared as      ''SRA_L'', ''SRA_M'' and ''SRA_H''. '''These names correspond to the names of the signal regions as declared in the analysis recast. The ordering MUST be the same as in the JSON file, otherwise, the exclusion limit will be calculated wrong. To make sure, please refer to the analysis description.''' ''VRtt_meff'' and ''CRtt_meff'' does not contain any signal region since the Validation and Control regions are not included in the analysis recast due to lack of information. If further help needed, one can use [http://madanalysis.irmp.ucl.ac.be/attachment/wiki/SRCombinations/write_histfactory_info.py write_histfactory_info.py] 

{{{
python write_histfactory_info.py -i FILE1.json FILE2.json FILE3.json
}}}
where -i refers to the interactive mode, which writes the file by giving you directions. The JSON files have to be named as in info file and placed in the same folder with the info file (''~/madanalysis5/tools/<PADofChoice>/Build/SampleAnalyzer/User/Analysis/atlas_xyz_00_00.info'')

In order to use [https://cds.cern.ch/record/2684863/files/ATL-PHYS-PUB-2019-029.pdf HistFactory], one needs to install [https://cds.cern.ch/record/2684863/files/ATL-PHYS-PUB-2019-029.pdf pyhf] package which is automatically installed via the following command

{{{
install pyhf
}}}

After these steps, all given signal region combinations are automatically calculated. Additionally, MadAnalysis constructs a global likelihood profile to combine all given HistFactory files with the same parameter of interest.