spa license fixes

.gitignore

@@ -30,6 +30,11 @@ build/
 # spa_c_files builds
 pvlib/spa_c_files/build*
 
+# spa_c_files source
+pvlib/spa_c_files/spa.c
+pvlib/spa_c_files/spa.h
+pvlib/spa_c_files/spa_tester.c
+
 # generated documentation
 # pvlib/sphinx/Docs/build/
 

README.md

@@ -24,14 +24,22 @@ Hopefully you're using [virtualenv](http://virtualenv.readthedocs.org/en/latest/
 pip install git+https://github.com/pvlib/pvlib-python.git
 ```
 
-Alternatively, ``git clone`` this repository and run
+Alternatively, ``git clone`` this repository, ``cd`` into it, and run
 
 ```
 pip install .
 ```
 
 Add ``-e`` to install in [develop mode](http://pip.readthedocs.org/en/latest/reference/pip_install.html#editable-installs).
 
+To use the NREL SPA algorithm, a pip install from the web cannot be used. Instead: 
+
+1. Download the pvlib repository from https://github.com/pvlib/pvlib-python.git
+2. Download the SPA files from [NREL](http://www.nrel.gov/midc/spa/)
+3. Copy the SPA files into ``pvlib-python/pvlib/spa_c_files`` 
+4. From the ``pvlib-python`` directory, run ``pip uninstall pvlib`` followed by ``pip install . ``
+
+
 Usage Example
 -------------
 ```

docs/sphinx/source/whatsnew/v0.1.0.txt

@@ -40,6 +40,7 @@ Other changes
 * Adding logging calls, removing print calls.
 * Improved PEP8 compliance.
 * Added ``/pvlib/data`` for lookup tables, test, and tutorial data.
+* Removed NREL's SPA code to comply with their license (:issue:`9`).
 
 
 Documentation

pvlib/spa_c_files/README.md

@@ -0,0 +1,34 @@
+README
+------
+
+NREL provides a C implementation of the solar position algorithm 
+described in 
+[Reda, I.; Andreas, A. (2003). Solar Position Algorithm for Solar Radiation Applications. 55 pp.; NREL Report No. TP-560-34302](
+http://www.nrel.gov/docs/fy08osti/34302.pdf).
+
+This folder contains the files required to make NREL's C code accessible
+to the ``pvlib-python`` package. We use the Cython package to wrap NREL's SPA 
+implementation. 
+
+** Due to licensing issues, you must download the NREL C files from their 
+[website](http://www.nrel.gov/midc/spa) **
+
+Download the ``spa.c`` and ``spa.h`` files from NREL, 
+and copy them into the ``pvlib/spa_c_files`` directory. 
+
+There are a total of 5 files needed to compile the C code, described below:
+
+* ``spa.c``: original C code from NREL 
+* ``spa.h``: header file for spa.c
+* ``cspa_py.pxd``: a cython header file which essentially tells cython which parts of the main header file to pay attention to
+* ``spa_py.pyx``: the cython code used to define both functions in the python namespace. NOTE: It is possible to provide user access to other paramters of the SPA algorithm through modifying this file 
+* ``setup.py``: a distutils file which performs the compiling of the cython code
+
+The cython compilation process produces two files:
+* ``spa_py.c``: an intermediate cython c file
+* ``spa_py.so``: the python module which can be imported into a namespace
+
+To process the original 5 files, 
+use the following shell command inside this folder
+
+ $ python setup.py build_ext --inplace

pvlib/spa_c_files/cspa_py.pxd

@@ -5,7 +5,7 @@ cdef extern from "spa.h":
 		int day            
 		int hour           
 		int minute         
-		int second  
+		double second  
 		double delta_ut1   
 		double delta_t     
 		double timezone    
@@ -27,7 +27,7 @@ cdef extern from "spa.h":
 		int function       
 
 		double zenith     
-		double azimuth180 
+		double azimuth_astro
 		double azimuth    
 		double incidence