| Larch: Data Analysis Tools for X-ray Spectroscopy

# 1. Downloading and Installation

The latest release version of Larch is 0.9.42.

Larch is in active and continuing development, and the intention is to tag a new release version every three to six months. Larch’s tools for XAFS data analysis and working with XRF data and XRF maps from X-ray microprobes are working and ready for general use. There may be bugs and unintended features, and some missing or incomplete desired features as we add new functionality.

## 1.1. Single-File Installers

For Windows, MacOSX, and Linux, Larch provides simple installers, available at Larch Binary Installers. These are self-contained files that will install a complete Python environment from Anaconda Python and all of libraries needed by X-ray Larch.. Installing Larch this way will be create a folder in your home folder called xraylarch (by default: you can change it). On Linux and MacOSX, this folder will be in the top-level of your home directory, while on Windows this folder will typically be in C:UsersYourNameAppDataLocalContinuumxraylarch. These installers will also create a folder called Larch on your desktop that contains links (or shortcuts or Apps) to many of the Larch GUI applications listed above in Table of Larch Applications and Programs. This includes tools for X-ray Absorption spectroscopy, X-ray fluorescence spectroscopy, and working with X-ray diffraction images.

Note that installing Larch only writes to files owned by the user account and does not require administrative privilege. It will not interfere with anything else on your system (like, say, system Python). You you can uninstall simply by removing xraylarch folder. The installers are fairly large (400 to 600 Mb), but includes an entire scientific python environment. Installing by the other means described below will not actually take less disk space, but will involve downloading many more smaller files, which may be an advantage for some people with poor connectivity.

Table of Larch Installers

> Operating System | installer
> --- | ---
> Windows (64 bit) | Larch for 64bit Windows
> Mac OSX (64 bit) | Larch for MacOSX
> Linux (64 bit) | Larch for Linux
> Source Code | source code (tar.gz)
> Docs and Examples (all systems) | Larch Docs and Examples

If you need a versions for 32-bit Windows or Linux, contact the authors.

For Windows, download the executable installer:

    xraylarch-0.9.42-Windows-x86_64.exe

and double-click to run it to install Larch

For Mac OSX, download the package installer:

    xraylarch-0.9.42-MacOSX-x86_64.pkg

and double-click to run it to install Larch.

For Linux, download the shell installer file, then open a Terminal, use cd to move to the download folder (typically Downloads) and run:

    bash xraylarch-0.9.42-Linux-x86_64.sh

Once installed, you will be able to upgrade to future versions of Larch using:

    conda update -yc GSECARS xraylarch

and you will be able to completely uninstall simply by removing the xraylarch folder in your home directory. Note that for Windows, The xraylarch folder is not typically put in your path, and so you would need to open a Command or Powershell window and do:

    C:\Users\YourName\AppData\Continuum\xraylarch\Scripts\conda.exe -yc GSECARS xraylarch

## 1.2. Installing with Anaconda Python

For those familiar with Python, Larch can be installed into an existing Python environment. We highly recommended using Anaconda Python for Larch. While Larch can be installed from source code with standard versions of Python, Anaconda Python makes getting and installing the many packages needed for Larch.

Anaconda Python provides a free and well-supported version of Python for scientific work with many useful packages included. By default, Anaconda Python installs into your own home folder (on Windows, this will be the APPDATA location, which is typically something like C:\Users\YourName\AppData\Local\Continuum\Anaconda3). As with the single-file installers above, installing Anaconda Python does not require extra permissions to install, upgrade, or remove components. Anaconda includes a robust package manager called conda that makes it easy to update the packages it manages, including Larch.

Start by installing the latest version of Anaconda Python from the Anaconda Downloads site. Python 3.7 or 3.6 is recommended. Larch will work with Python 2.7 too, but we’re not promising it will work past version 0.9.41.

Once that is installed, you can open a Terminal (on Linux or Mac OSX) or the Anaconda prompt (on Windows) and type:

    conda install -yc GSECARS xraylarch

to install Larch.

To make a Larch folder on your desktop with shortcuts (Windows or Linux) or Applications (MacOS) for the main Larch applications, you can then type:

    larch -m

If that complains that it does not find larch, you may have to do something like:

    $HOME/xraylarch/bin/larch -m

from Linux or MacOSX or:

    %APPDATA%\\Continuuum\xraylarch\Scripts\larch.exe -m

from Windows.

By using Anaconda Python, updates are very easy for us to make and for you to install. As new releases of Larch and the required packages are released, you can get the latest versions with:

    conda update --all

## 1.3. Python Versions: 3.7, 3.6, or 2.7?

As of this writing (February, 2019) there are three main supported versions of Python: Version 3.7, Version 3.6, and Version 2.7. We have moved to using Python 3 by default. The installers above use Python 3.6. Most of the dependencies and tools will work with Python 3.7, but we have not gotten all the tools working together with Python 3.7 yet. We expect that Larch 0.9.43 will use 3.7.

Up to version 0.9.41, Larch still works with Python 2.7. With the release of Larch 0.9.41, we stopped testing and supporting Python 2.7, but promised to not intentionally break anything until 0.9.42 is relasead.

With Larch version 0.9.42, Python 2.7 is no longer supported. You may be able to get Larch to work with Python 2.7 or 3.5, but we cannot help you if things do no work properly.

## 1.4. Source Installation

For Python-savvy users, Larch can be installed from source. You can use either the source code (tar.gz) or from Larch releases (github.com). In addition, you can use git to grab the latest development version of the source code:

    git clone http://github.com/xraypy/xraylarch.git

With the source kit unpacked using tar or zip, you should be able to install Larch using python setup.py install. This should automatically use pip to install any required dependencies as well as Larch itself. Depending on your platform and version of Python, you may need elevated permissions as from sudo to install Larch to a system folder.

There are several required packages and a few “highly recommended” packages for Larch. These are listed in the next section.

### 1.4.1. Prerequisites

Larch requires Python version 3.6 or higher. In addiion, many Python packages are required for Larch to work. These are listed in the table below.

Table of Larch Dependencies This lists the packages that are either required for Larch or required for some portion of Larch functionality to work. The required packages and several of the recommended packages will normally be installed by default or are easily available from with conda or pip.

> Package name | min version | status, notes
> --- | --- | ---
> numpy | 1.15 | required
> scipy | 0.19 | required
> six | 1.10 | required
> matplotlib | 2.0 | required
> sqlalchemy | 0.9 | required
> h5py | 2.8 | required
> scikit-learn | 0.18 | required
> pillow | 3.4 | required
> peakutils | 1.3.0 | required
> requests | 2.1 | required
> asteval | 0.9.13 | required
> lmfit | 0.9.12 | required
> uncertainties | 3.0.3 | required
> pyyaml |  | required
> psutil |  | required
> termcolor |  | required
> wxpython | 4.0.3 | required for GUIs, plotting
> wxmplot | 0.9.34 | required for plotting
> wxutils | 0.2.3 | required for GUIs
> pyepics | 3.3.3 | needed for using Epics
> scikit-image |  | needed for tomography maps
> tomopy | 1.3.0 | recommended for tomography
> pyFAI |  | needed for XRD
> fabio |  | needed for XRD
> PyCifRW |  | needed for XRD
> epicsscan |  | needed for epics scanning
> psycopg2 |  | needed for epics scanning
> silx |  | needed to read Spec files

These are all available from PyPI (the Python Package Index), and for Anaconda Python 3.7 and 3.6. The packages not included with core Anaconda packages are available on the GSECARS conda channel, and will be installed with conda install -c GSECARS xraylarch. If you’re installing from source or using a Python distribution other than Anaconda, all these packages are also available from PyPI and can be installed with pip install <packagename> or conda install -c GSECARS <packagename>.

### 1.4.2. Optional Modules

There are a few packages that are required only for some more specialized uses of Larch that may not be important for everyone using Larch. For example, the advanced and in-development X-ray diffraction analysis capabilities require the following packages:

> fabio, pyFAI, PyCifRw

Some x-ray computed tomography capabilities are available, and require the packages:

> tomopy, scikit-image

These are generally supported and available with Python 3.6, and are included with the binary installers above, or on the GSECARS anaconda.org channel.

Some Epics-based data collection tools use Larch, and require:

> pyepics, psycopg2, epicsscan

As with the other packages listed above, these are either available from the GSECARS anaconda channel or from PyPI.

To be clear, most of Larch will work fine without these modules installed, but the corresponding functionality will not be available.

### 1.4.3. Installation from Source

If installing from source, first unpack the source distribution kit, move into the created xraylarch-VERSION directory, and type:

    python setup.py install

## 1.5. Documentation and Examples

The source kit includes sources for documentation in the docs folder and several examples (including all those shown in this documentation) in the examples folder. These are also available separately at Larch Docs and Examples.

## 1.6. Citing Larch

Currently, the best citation for Larch is M. Newville, Larch: An Analysis Package For XAFS And Related Spectroscopies. Journal of Physics: Conference Series, 430:012007 (2013). [Larch_2]

## 1.7. Funding and Support

Larch development at the GeoScoilEnviroCARS sector of Center for Advanced Radiation Sources at the University of Chicago has been supported by the US National Science Foundation - Earth Sciences (EAR-1128799), and Department of Energy GeoSciences (DE-FG02-94ER14466). In addition, funding specifically for Larch was granted by the National Science Foundation - Advanced CyberInfrastructure (ACI-1450468).

## 1.8. Acknowledgements

Larch was mostly written by and is maintained by Matt Newville <newville@cars.uchicago.edu>. Bruce Ravel has an incalculable influence on the design and implementation of this code and has provided countless fixes for serious problems in design and execution in the early stages. More importantly, Larch would simply not exist without the long and fruitful collaboration we’ve enjoyed. Margaret Koker wrote most of the X-ray diffraction analysis code, and much of the advanced functionality of the GSECARS XRF Map Viewer. Mauro Rovezzi has provided the spec-data reading interface. Tom Trainor had a very strong influence on the original design of Larch, and helped with the initial version of the python implementation. Yong Choi wrote the code for X-ray standing wave and reflectivity analysis and graciously allowed it to be included and modified for Larch. Tony Lanzirotti and Steve Sutton have provided wonderful and patient feedback on many parts of Larch, espcially for XANES processing and testing of the XAS Viewer GUI.

Because Larch began as a rewrite of the Ifeffit XAFS Analysis Package, it also references and builds on quite a bit of code developed for XAFS over many years at the University of Chicago and the University of Washington. The existence of the code and a great deal of its initial design therefore owes a great thanks to Edward Stern, Yizhak Yacoby, Peter Livens, Steve Zabinsky, and John Rehr. More specifically, code written by Steve Zabinsky and John Rehr for the manipulation of results from FEFF and for the calculation of thermal disorder parameters for XAFS are included in Larch with little modification. Both Feff6l and Feff8l, the product of many man years of effort by the Feff group led by John Rehr, are included in Larch. A great many people have provided excellent bug reports, feedback, in depth conversations, and suggestions for making Ifeffit better, including on the ifeffit mailing list. Many of these contributions have found their way into Larch.

Larch includes calculations for anomalous cross-sections based on the work of Cromer and Libermann, as implemented by Sean Brennan and Paul L. Cowen. Their code is included in Larch with only minor changes. Code to store and read the X-ray Scattering data from the Elam Tables was modified from code originally written by Darren S. Dale. Refined values for anomalous scattering factors have been provided directly by Christopher T. Chantler. Further details of the origin of much of the tabularized X-ray data is given in 10.

As Larch depends on the fantastic scientific librarie written and maintained in python, especially the numpy, scipy, and matplotlib, the entire scientific python community deserves a hearty thanks. In particular, Larch uses the lmfit library, which began as part of Larch but was spun off into a standalone, general purpose fitting library that became useful for application areas other than XAFS, and has benefited greatly from numerous collaborators and added many features that Larch, in turn, has been able to depend on.

## 1.9. License

Except where explicitly noted in the individual files, the code, documentation, and all material associated with Larch are distributed under the BSD License:

    BSD-2-CLAUSE LICENSE

    Copyright, Licensing, and Re-distribution
    -----------------------------------------

    Unless otherwise stated, all files included here are copyrighted and
    distributed under the following license:

    Copyright (c) 2010-2019 Matthew Newville, The University of Chicago
    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright notice, this
      list of conditions and the following disclaimer.

    * Redistributions in binary form must reproduce the above copyright notice,
      this list of conditions and the following disclaimer in the documentation
      and/or other materials provided with the distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
    AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
    FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
    DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
    SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
    OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
    OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

References

[Larch_2] | M. Newville. Larch: An Analysis Package For XAFS And Related Spectroscopies. Journal of Physics: Conference Series, 430:012007, 2013. doi:10.1088/1742-6596/430/1/012007.