Update docs

Author: davistdaniel

docs/source/index.rst

@@ -67,10 +67,11 @@ Using EPRpy
 ----------------------
 
 .. toctree::
-   :maxdepth: 2
+   :maxdepth: 1
    :caption: User guide
 
 
    loading
+   processing
    EprData
 

docs/source/loading.rst

@@ -15,4 +15,4 @@ Data can be loaded into an ``EprData`` object by using the ``load(filepath)`` fu
   epr_data = epr.load('tempo.DSC')
 
 
-``epr_data`` is an :doc:`EprData <EprData>` data object with various accessible attributes. For instance the loaded data can be accessed by ``epr_data.data``.
+``epr_data`` is an :doc:`EprData <EprData>` data object with various accessible attributes. For instance. the loaded data can be accessed by ``epr_data.data``.

docs/source/processing.rst

@@ -0,0 +1,40 @@
+Operations on data
+============================
+
+After loading the data into an ``EprData`` object, following functions can be used to perform various operations on the data. Since the data is stored as NumPy arrays, all artihmetic operations 
+whihc are valid on NumPy arrays are also valid on  attributes of ``EprData`` which are NumPy arrays, such as ``data``, ``x`` and ``y``.
+Please note that, unless otherwise specified, all operations on the data are done in place i.e. a new object is not returned. After each operation, a history entry is added to the history of the ``EprData`` object. 
+Calling the ``undo`` method of any ``EprData`` object will return the ``EprData`` object before the last operation on the data.
+
+Scaling
+************
+Data in an ``EprData`` object can be scaled between two values using the ``scale_between`` method. 
+There are two optional inputs ``min_val`` and ``max_val``, which correspond to the minimum and maximum value of the range within which the data will be scaled. 
+If no inputs are given, the data is scaled between 0 and 1.
+
+Computing Integrals
+***********************
+Integrals can be calculated using the ``integral`` method of the ``EprData`` class. 
+Since CW-EPR data is usually acuqired as firtst-derivatives, the function should be called twice for a double integral calculation. 
+
+Baseline Correction
+***********************
+Baseline correction in EPRpy supports 1D and 2D data and allows for interactive selection of baseline points. Baseline points in case of 2D data are selected using the first slice of the data.
+The baseline can be fitted using linear, polynomial, or spline methods. To correct the baseline, ``baseline_correct`` method of the ``EprData`` class can be used.
+Basline correction accepts various inputs :
+
+* *interactive* : If set to True, this will plot the data with an option to sleect points interactively. These points will then be used for the calculatinh the baseline.
+* *npts* : Another way of specifying points. When *interactive* is set to False, npts is equal to the number of points at the start and end of the data which is used for baseline correction.
+* *method* :  Should be one of 'linear', 'polynomial' and 'spline'.
+* *order* : Specifies the polynomial order in case of *method* 'polynomial'.
+* *spline_smooth* : Smoothing factor of the spline, in case of *method* 'spline'.
+
+Selecting a region
+********************
+This operation returns a new ``EprData`` object, which corresponds to selected region of the data (or spectrum). The operation is always carried out on the last axis of the data 
+and needs a list of indices as input which corresponds to the desired region.
+
+Undoing changes
+*******************
+Any data operation can be undone and the original ``EprData`` object just before the operation can be obtained by using the ``undo`` method of the ``EprData`` class.
+Note that any previous ``EprData`` object can be accessed by using the ``history`` attribute of the ``EprData`` object.