lenspack 1.0.0
builtins Author: Austin Peel, Email: austin.peel@cea.fr, Year: 2019, A collection of weak lensing tools in Python
License: MIT

# lenspack
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---
> Author: <a href="http://www.cosmostat.org/people/austin-peel" target="_blank" style="text-decoration:none; color: #F08080">Austin Peel</a>  
> Email: <a href="mailto:austin.peel@cea.fr" style="text-decoration:none; color: #F08080">austin.peel@cea.fr</a>  
> Year: 2019  
---

This repository is a collection of python codes useful for the weak-lensing analysis of galaxy catalogs and shear/convergence maps. The full documentation can be found [here](https://austinpeel.github.io/lenspack/index.html "lenspack documentation").

## Contents

In progress.

## Dependencies

* python (version 3.5 or later)
* numpy
* scipy
* astropy
* [emcee](https://emcee.readthedocs.io/en/stable/ "emcee") (optional)
* [nicaea](https://github.com/CosmoStat/nicaea "nicaea") (optional)
* [iSAP](http://www.cosmostat.org/software/isap "iSAP") (optional)

## Installation

Clone this repository to your local machine. You might find it helpful to do this in a virtual environment in order to keep a clean workspace.
```
$ git clone https://github.com/cosmostat/lenspack.git
```
A new directory `lenspack` will be generated. Navigate into it.
```
$ cd lenspack
```
Run the setup script to install lenspack and its necessary dependencies.
```
$ pip install .
```

The package will also soon be available to install directly using pip.

## Examples

### Peak detection

Suppose you have a galaxy catalog `cat` containing sky position columns `ra` and `dec`, along with ellipticity components `e1` and `e2`. You can bin the galaxies into pixels, invert the shear to obtain convergence (Kaiser & Squires, 1993), detect peaks above a given threshold, and plot the result as follows.

```python
import matplotlib.pyplot as plt
from lenspack.utils import bin2d
from lenspack.image.inversion import ks93
from lenspack.peaks import find_peaks2d

# Bin ellipticity components based on galaxy position into a 128 x 128 map
e1map, e2map = bin2d(cat['ra'], cat['dec'], v=(cat['e1'], cat['e2']), npix=128)

# Recover convergence via Kaiser-Squires inversion
kappaE, kappaB = ks93(e1map, e2map)

# Detect peaks on the convergence E-mode map
x, y, h = find_peaks2d(kappaE, threshold=0.03, include_border=True)

# Plot peak positions over the convergence
fig, ax = plt.subplots(1, 1, figsize=(7, 5.5))
mappable = ax.imshow(kappaE, origin='lower', cmap='bone')
ax.scatter(y, x, s=10, c='orange')  # reverse x and y due to array indexing
ax.set_axis_off()
fig.colorbar(mappable)
plt.show()
```

![peaks](./examples/figures/peaks.png)

### Wavelet transform

Take the starlet transform of an image using two different methods. Compare results to the equivalent aperture mass filter at a given scale.

```python
import numpy as np
import matplotlib.pyplot as plt
from lenspack.image.transforms import starlet2d, mr_transform
from lenspack.image.filters import aperture_mass

# Generate a test image
img = np.random.randn(256, 256)

# Take the starlet transform with 5 wavelet scales
st = starlet2d(img, nscales=5)
mrt = mr_transform(img, nscales=5)  # The iSAP mr_transform binary is required for this wrapper function to work

# Compute the aperture mass map at scale 4 using the starlet filter
apm = aperture_mass(img, theta=2**4, filter='starlet')

# Plot
fig, (ax1, ax2, ax3) = plt.subplots(1, 3, figsize=(12, 5))
ax1.imshow(st[3], cmap='magma')
ax2.imshow(mrt[3], cmap='magma')
ax3.imshow(apm, cmap='magma')
for ax in (ax1, ax2, ax3):
    ax.set_axis_off()
```

![wavelet transfrom](./examples/figures/wavelet_transform.png)