| Larch: Data Analysis Tools for X-ray Spectroscopy

# 1. Downloading and Installation

The latest release version of Larch is 0.9.37.

Larch is in active and continuing development, and the intention is to tag a new release version every three to six months. Of course, there may be bugs and unintended features, and some missing or incomplete desired features as we add new functionality. Still, most of what is in Larch for XAFS data analysis and working with XRF maps from X-ray microprobes is working and ready for use.

## 1.1. Single-File Installers

For Windows, MacOSX, and Linux, Larch now comes with simple installers, available at Larch Installers (cars.uchicago.edu). These are self-contained files that will install a complete Python environment from Anaconda Python and all of X-rayLarch onto your computer. Installing Larch this way will be create a folder in your home folder called xraylarch by default (you can change it). This does not require administrative privilege and will not interfere with anything on your system – you can uninstall simply by removing this folder. The installers are fairly large (300 to 500 Mb), but includes an entire scientific python environment. Installing by the other means described below will not take less disk space.

Table of Larch Installers

> Operating System | installer
> --- | ---
> Windows (64 bit) | Larch for 64bit Windows
> Windows (32 bit) | Larch for 32bit Windows
> Mac OSX (64 bit) | Larch for MacOSX
> Linux (64 bit) | Larch for Linux
> Docs and Examples (all systems) | Larch Docs and Examples

For Windows, download the appropriate executable installer corresponding to the architecture of your OS, and run it. Most modern computers (including Windows 10) will be running 64-bit Windows. A 32-bit version is provided for older systems, but support for this may be dropped in late 2018.

For Mac OSX or Linux, download the appropriate file then open a Terminal (Applications->Utilities->Terminal on Mac OSX), use cd to move to the download folder (typically cd Downloads) and run:

    bash xraylarch-0.9.37-MacOSX-x86_64.sh

or:

    bash xraylarch-0.9.37-Linux-x86_64.sh

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

    conda update xraylarch

and you will be able to completely uninstall simply by removing the xraylarch folder in your home directory.

On Windows and Mac OSX, the installer will create a Larch folder on your Desktop containing links to many of the Larch GUI applications listed above in Table of Larch Applications and Programs.

A key advantage of using Anaconda is that once installed, updates can be installed with:

    conda update -yc GSECARS xraylarch

As of this writing, some functionality – notably X-ray diffraction – may need additional libraries installed, and some of these libraries may not be available for Python3.6 or for all platforms. We’re working on this, but if you need help, please contact us.

## 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\Anaconda2). 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.

Begin by installing the latest version of Anaconda Python – either Python 2.7 or 3.6 should work (though Python 3.6 may have undiscovered bugs) from the Anaconda Downloads site. 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. On Windows or Mac OSX, then type:

    larch_makeicons

to make a Larch folder on your desktop with shortcuts (Windows) or Applications (MacOS) for the main Larch applications.

One advantage of Anaconda Python is that it makes updates very easy. 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: 2.7 or 3.6?

As of this writing (March, 2018) there are two main supported versions of Python: Version 2.7 and Version 3.6. Larch works with both versions of Python. We invite Python-savvy users to try out Larch with Python 3.6. We believe most things are working with Python 3.6, and are actively using Larch with Python 3.6, but there may be some undiscovered bugs. We are eager to migrate Larch so that it works only with Python 3.6 and higher so that we can take advantage of many language features not available in earlier versions. Following the schedule of many scientific Python libraries and tools, we expect to make this transition in early 2019.

Currently, the installers above are built with Python 2.7. We

## 1.4. Source Installation

For Python-savvy users, Larch can be installed from source code. The latest releases of the source code will be available 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

### 1.4.1. Prerequisites

Larch requires Python version 2.7 or 3.6. In addiion, the following Python packages are all required for Larch to work:

> numpy, scipy, matplotlib, h5py, peakutils, pillow, psutil, requests, sqlalchemy, six, termcolor, wxPython, lmfit, asteval, wxmplot, wxutils.

These are all available from PyPI (the Python Package Index), and for Anaconda Python 2.7 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

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.

At this writing (March, 2018), we do not have supported packages for Windows for fabio, pyFAI, or tomopy. You may be able to install fabio and pyFAI separately, and we are working on these packages.

### 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). [Install_1]

## 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 had 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 than that, 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. 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.

Having begun as a rewrite of the Ifeffit XAFS Analysis Package, Larch 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. 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 includes code from Jonathan J. Helmus to implement robust setting of Parameter bounds as described in the MINUIT User’s guide. Till Stensitzki wrote the code for improved, brute-force estimates of confidence intervals, and Christopher Deil provided many valuable suggestions for improving the parameterized fitting used in Larch. Eric O. Lebigot’s uncertainty package for automated calculation and propagation of uncertainties is also included in Larch, with slight modification.

## 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) 2010-2017 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

[Install_1] | 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.