- Purpose
**Obtaining the package**- What's in the box...
- The iData objects (iFit/@iData): the core data set
- The iFunc objects (iFit/@iFunc): the core model
- The optimization library (iFit/Optimizers)
- The fit functions/models (iFit/Models)
- The lower level import routines (iFit/Loaders)
- The documentation (iFit/Docs)
- Example data files (iFit/Data)
- Interfaces with other software and Graphical front-ends (iFit/GUI)

- Ok, let's start !
- For beginners
- Help me !
- Credits, Links and Disclaimer

Welcome to the iFit Data Analysis library !

<ifit.mccode.org>

"Simple methods to be used for complex data analysis"

Main functionalities are

[ iData Load Plot Math Fit

Users having installed version 1.8 are encouraged to

(both source code and standalone programs)

The spirit of the library is to include object definitions, with a set of methods that provide all the means to perform the usual data analysis procedures.

You need Matlab to make use of the source package. The stand-alone (binary) package does not require Matlab, but you will need the Matlab Compiler Runtime (refer to the Install page). The Python interface requires either Matlab or the iFit standalone package to be installed, as well as

The package is currently available from the ifit.mccode.org web site:

- source package for all platforms, requires a Matlab license to run [ zip, 29 Mb, Changes and Bugs].

- standalone
packages (no need for a Matlab license) for
Linux, Windows and Mac OS X are available from the Install
page. You will then use the iFit standalone interface to the package
(a terminal/command window providing Matlab/iFit
capabilities).

- [ McCode
Git ][ older
versions ][ TechDoc
]

Please register to the ifit-users mailing list.

What you will handle mainly deals with iData and iFunc objects. Please start to read these pages first, as well as the Quick Start page if you're in a hurry.

The iData
objects have been defined in order to perform the following
operations seamlessly:

- Load any text formatted file, and a large set of binary format files
- Display object information, including metadata from the
original file

- Plot the object Signal in a simple view for 1D, 2D and 3D objects
- Perform mathematical operations using objects (=-/* trigonometric projections integration re-binning...)
- Fit a parametrized model to the object
Signal, which makes use of the Optimizers
and Models libraries.

- Save the object into a set of output formats

An extended list of iData methods is
available in the Methods page. In
addition, a few dedicated applications of these methods is
presented in the Treatment page, for
instance for neutron scattering.

#### The iFunc objects (iFit/@iFunc): the core model

The iFunc objects hold models
(mathematical expressions that return a vector, matrix, ...)
value, as a function of a parameter set, and axes. You can
easily create new models, or use those from the Models page, and combine them to build
more complex models. The objects support most usual mathematical
operators.

A set of optimization routines has
been gathered in the Optimizers
part of iFit. It enables to choose and compare how different
optimization methods can solve a problem. This library is used
transparently by the iData fits method,
but it may also be used independently.

#### The fit
functions/models (iFit/Models)

A set of parametrized models is given in the Models part of iFit in order to fit some
imported data and find best parameter sets which describe it.
These functions may be used by the fits
method. All these models are iFunc
objects. There are very advanced Models to compute for instance 4D phonon dispersions
using *ab-initio* codes, and other simpler analytical
methods.

The file import method used by iData
is performed on a lower level by the Loaders
part of iFit. Its purpose is to import any binary or text file,
without knowing its format. A number of post-import wrappers exist
in order to reshape the imported data to match specific needs.
These wrappers are very short to write.

If needed, other importation methods should be added there, to be able to handle more formats. This library is used transparently by the iData load method, but it may also be used independently to produce simple structures describing the data files (even though we do not recommend this).

#### The
documentation (iFit/Docs)

The documentation is given as web pages, and all methods/functions
have their own embedded help. To access it use:

#### Example data
files (iFit/Data)

Some Data files are given as examples to be
used along the documentation web pages and in the Quick Start.

#### Interfaces with
other software and Graphical front-ends (iFit/GUI)

Specific interfaces have been written in order to use iFit
transparently for end-user applications:

If needed, other importation methods should be added there, to be able to handle more formats. This library is used transparently by the iData load method, but it may also be used independently to produce simple structures describing the data files (even though we do not recommend this).

>> doc(iData)A list of all available iData methods is also available, and can be directly accesed with

>> methods(iData)The documentation currently contains the following pages:

- Changes: Version releases,
**Changes and Bugs**list. - Credits: Credits, Licensing and contributions from others.
- Fit: how to fit data sets onto mathematical models and find the best parameter set
- iData: the description of the fundamental data set object used in iFit, properties and how to handle it
- iFunc: the description of the fundamental model object used in iFit, properties and how to handle it
- Loaders: how to import data files into structures, which can be converted into iData afterwards. This is a sub-library which you should only use if you need the data NOT to be an object (but you then loose most of the iData capabilities).
- Models: model functions that cab
be use for data fitting. A function maker tool is also
provided. Specialized models provide phonon dispersions,
Rietveld refinement, small angle scattering.

- index: This iFit Welcome page.
- iFit: the interface used in the
stand-alone distribution.

- Install: the installation page.
- Optimizers: the low level optimization methods.
- Load: how to load data set directly as iData objects. This is what you should use.
- Math: all mathematical operations and related data handling to apply on iData objects.
- McStas: an interface with the McStas neutron scattering ray-tracing simulation code for simulation, scanning and optimization.
- Methods: a list of all available methods for iData objects.
- Plot: many ways to plot the iData objects.
- QuickStart: where you should start (a quick tutorial).
- Save: Saving iData objects into many file formats.
- Treatment: a set of
methodologies applied to specific cases, for instance neutron
scattering (dynamic structure factors).

- PyFit: an interface which exposes transparently all iFit methods and objects into Python/NumPy.
- Technical documentation

- McStas: a wrapper to run
simulations or optimize McStas
and McXtrace
instruments.

**ResLibCal**: compute the neutron TAS spectrometer resolution ellipsoid (ResCal/ResLib merge)**Sqw_Phonons**: Phonon dispersion from*ab-initio*force estimate and dynamical matrix

- iFunc/Model Builder: a dialogue to create iFunc fit function/models.
- iFit standalone: the prompt interface used in the no-Matlab-license release. Can execute any Matlab expression, scripts, handle iData and iFunc objects, optimizers, plotting, ...
- PyFit: using iFit transparently from Python/NumPy.

To install the package, refer to the
Install page, you just need Matlab.

If you want a quick example, refer to the Quick Start page. Otherwise, the typical usage would be:

If you want a quick example, refer to the Quick Start page. Otherwise, the typical usage would be:

Start Matlab... or iFit stand-alone

>> addpath(genpath('/some/path/to/iFit')); % not needed for the stand-alone version

>> a = iData([ ifitpath 'Data/ILL_IN6.dat' ]);

>> plot(log10(a))

>> b=2*a+log(a)

>> plot(gauss2d)

>> parameters=fits(a,gauss2d)

>> saveas(a,'filename.pdf')

If you do not know Matlab already,
you will discover that using the iFit library does not require
advanced IT knowledge. The general syntax are rather intuitive,
and all methods are able to tolerate (and correct) most of the
user mistakes. In this respect, when some of the input parameters
are missing, sensible choices can be made automatically. You can
look at the iFit page, where a short
Matlab introduction is available.

If you have used in the past the MFit/MView suite, you will find that this library has the same scope, but omitting the user interface.

If you have used the Spec1d object, you will quickly find that the iFit follows exactly the same syntax.

If you come from the Python world, you will find out that the iFit syntax is pretty close. We provide for you a Python interface to iFit which exposes all iFit objects and methods into Python. Refer to the PyFit page.

If you have used in the past the MFit/MView suite, you will find that this library has the same scope, but omitting the user interface.

If you have used the Spec1d object, you will quickly find that the iFit follows exactly the same syntax.

If you come from the Python world, you will find out that the iFit syntax is pretty close. We provide for you a Python interface to iFit which exposes all iFit objects and methods into Python. Refer to the PyFit page.

>> doc(iData)and help pages for each function/method, which you can access with e.g.

>> doc(iFunc)

>> methods(iData)

>> help iDataA Tutorial (Jan 2012) is available as PDF presentations with exercises.

>> help iData/load

>> help iFunc

You may also search this whole documentation (using Google): Finally, the whole Matlab documentation is available on-line for free, especially to complement the standalone limited help system.

If you find new bugs please send them to me [farhi (at) ill.fr] with:

- your Matlab version
- the iFit version which you can get from the Matlab command version(iData)

- the script/command that reproduces the error together with any required external data file
- a copy of the error messages produced by the script/command.

- a smile ;-)

You may register by entering your email address and press subscribe:

Substantial contributions from Y. Debab and P. Willendrup.

If you produce scientific output using iFit, I'd appreciate if you cite the following reference:

- E. Farhi, Y. Debab and P. Willendrup, J. Neut. Res., 17 (2013) 5. DOI: 10.3233/JNR-130001
- E. Farhi, The iFit data analysis library, ILL, Computing for Science (2011-2012) <http://ifit.mccode.org>.

See the Credits page for more information on contributions, including licensing.

A set of links to related packages is also included there.

Disclaimer:

This software is experimental, and should not be considered bullet-proof. In particular, expect many bugs - which should be reported to me [farhi (at) ill.fr] if you want them to be fixed quickly. Also, this prototype is known to be slow. This will be improved gradually...