I. PACKAGE REQUIRED

1.  NUMPY
   

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	a.	sudo apt-get install python-numpy

2.  ASTROPY
   

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	a.	Using pip
			pip install --no-deps astropy
	b.	Anaconda python distribution
			conda install astropy

3.  HEALPY
   

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	a.	Using pip
			pip install --user healpy
			To upgrade:
			pip install --user --upgrade healpy
	b.	curl -O https://pypi.python.org/packages/source/h/healpy/healpy-1.9.1.tar.gz
			To build:
			tar -xzf healpy-1.9.1.tar.gz
			pushd healpy-1.9.1
			python setup.py install --user
			popd

4.  EPHEM
   

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	a. pip install ephem

II. INSTALLATION GUIDELINES

To download all the codes kindly run the following command in the terminal:

git clone https://github.com/emvarun/followup-and-location

III. WORKING WITH THE CODE: STEP BY STEP

1. Obtaining the fits files

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The released set of fits file can be downloaded from 'http://www.ligo.org/scientists/first2years/'. Note: The patches are dependent on the detector senstivity, thus, the two detector patches of 'fits-2015' are for an LIGO-O1 detector sensitivity, while the same for 'fits-2016' are with LIGO-O2 detector sensitivity. Thus, the two sets are fundamentally different

2. Edit dates

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The following step is to edit the dates of trigger in the original fits file header to the period of interest -- say LIGO observational period. Run the file in the terminal as

python EditDate.py

The user will be prompted if they want to change the date of injection in the released fits file to a period of their interest. The new files will be saved in the same directory with the released set of files but will have a 'Mod-Date' suffixed in their name. The user is free to move them to a convenient folder of his interest. Note: Update the variable 'folddir' in 'params.py' file to the folder directory which contains all the fits file one wishes to analyse over. Please change the variable accordingly.

3. Analysis

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The locations that one wishes to analyse can be added in the 'Observatory.py' file. To remove locations one can simply comment them out. Once the folder directory 'folddir' is updated. One can proceed with the analysis of the fits files. The variables involved are listed in 'params.py'. The file 'Sky_patch.py' evaluates the probability covered upto N square degrees for a given fits file. The file 'Loop_SkyPatch.py' loops over all the files in the folder 'folddir', and returns a text file which contains the probability covered upto the given N square degrees 'NsqDeg', for all the fits files one runs over. To run this part, open the terminal and once in the directory where these codes exist, run

python Loop_SkyPatch.py

One will get the output files in the directory given by variable 'Location_Datafiles' in the 'params.py' file. The file 'params.py' contains the description of all the variables involved.

4. Post-Analysis: Plots and Tables

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The file 'Results.py' reads the output data files from the previous step. One needs to run

python Coverage_Analysis.py 

The code returns a boxplot which compares the performance of different locations for all the fits files. A table is returned which contains the mean and median of the probability distribution for a given location and the first and third quartile values. The parameters taken by the function 'ReadData' are explained below. The variable 'IfAllNDet' is a bool value parameter which if True analyses and plots all the events irrespective of the number of detectors involved. However, when set as False, it reads only the those events which are recovered by the number of detectors defined by 'Ndets'. The variable 'PeriodComb' is also a bool variable which when initialized as True, considers only those events in the analysis that occured during the period of the year defined by 'Period'. Eg. if period is set to 'Sep', the analysis will consider all events that occur in August, September and October. The variable 'yaxisTop' defines the upper probability limit of each of the subplots. This has to be editted accordingly when one makes any change to the 'NsqDeg' variable.

For any queries feel free to contact me Varun Srivastava (varun.srivastava@students.iiserpune.ac.in)