OneCovariance is python package (with some C++ for the heavy lifting) for the calculation of the covariance matrix of photometric large-scale structure surveys. It can produce the covariance matrix for all the 2-point statistics used within the Kilo-Degree-Survey (KiDS), that is configuration space statistics, bandpowers and COSEBIs. All these observables are derived from projected Fourier space quantities. The code is flexible enough to read in the ingredients from a harmonic space covariance matrix and produce one of the mentioned statistics (whether these are optimal for the considered case is a different question).

Documentation, Installation and Examples

The installation steps, documentation and examples are all provided at onecovariance.readthedocs.io.

Using the conda environment

For starters you first clone the directory via:

git clone git@github.com:rreischke/OneCovariance.git

or

git clone https://github.com/rreischke/OneCovariance.git

Then navigate to the cloned directory

cd OneCovariance
conda env create -f conda_env.yaml
conda activate cov20_env
pip install .

On some Linux servers you will have to install gxx_linux-64 by hand and the installation will not work. This usually shows the following error message in the terminal: gcc: fatal error: cannot execute 'cc1plus': execvp: No such file or directory If this is the case just install it by typing

 conda install -c conda-forge gxx_linux-64

and redo the pip installation.

Not using the conda environment

If you do not want to use the conda environment make sure that you have gfortran and gsl installed. Note that there is an issue with pybind11 when using python >= 3.13, so make sure to use a version below that for the moment. You can install both via conda:

conda install -c conda-forge gfortran
conda install -c conda-forge gsl
conda install -c conda-forge gxx_linux-64
git clone git@github.com:rreischke/OneCovariance.git
cd OneCovariance    
pip install .

Once you have installed the external package via pip install the code simply runs by using the config.ini where all parameters are stored and explained. Running the script

python covariance.py

will run the code using the settings in the standard configuration file config.ini.

Using the code

If you use the OneCovariance code, please cite the corresponding paper. In there, you can also find the main equations used in the computation as well as a general review on covariance matrix computation.