Merge pull request #129 from wholmgren/raise-valueerror-in-relativeairmass

Raise ValueError in relativeairmass

Author: wholmgren

docs/sphinx/source/whatsnew/v0.3.0.txt

@@ -33,6 +33,9 @@ API changes
   variable conventions.
 * ``irradiance.total_irrad`` now follows the variable conventions.
   (:issue:`105`)
+* ``atmosphere.relativeairmass`` now raises a ValueError instead of
+  assuming ``'kastenyoung1989'`` if an invalid model is supplied.
+  (:issue:`119`)
 
 
 Enhancements

pvlib/atmosphere.py

@@ -1,14 +1,10 @@
 """
-The ``atmosphere`` module contains methods to calculate 
-relative and absolute airmass and to determine
-pressure from altitude or vice versa.
+The ``atmosphere`` module contains methods to calculate relative and
+absolute airmass and to determine pressure from altitude or vice versa.
 """
 
 from __future__ import division
 
-import logging
-pvl_logger = logging.getLogger('pvlib')
-
 import numpy as np
 
 APPARENT_ZENITH_MODELS = ('simple', 'kasten1966', 'kastenyoung1989',
@@ -29,7 +25,7 @@ def pres2alt(pressure):
     Returns
     -------
     altitude : scalar or Series
-        Altitude in meters above sea level 
+        Altitude in meters above sea level
 
     Notes
     ------
@@ -51,22 +47,20 @@ def pres2alt(pressure):
 
     "A Quick Derivation relating altitude to air pressure" from Portland
     State Aerospace Society, Version 1.03, 12/22/2004.
-
     '''
 
     alt = 44331.5 - 4946.62 * pressure ** (0.190263)
     return alt
 
 
-
 def alt2pres(altitude):
     '''
     Determine site pressure from altitude.
 
     Parameters
     ----------
     Altitude : scalar or Series
-        Altitude in meters above sea level 
+        Altitude in meters above sea level
 
     Returns
     -------
@@ -100,29 +94,28 @@ def alt2pres(altitude):
     return press
 
 
-
 def absoluteairmass(airmass_relative, pressure=101325.):
     '''
-    Determine absolute (pressure corrected) airmass from relative 
+    Determine absolute (pressure corrected) airmass from relative
     airmass and pressure
 
-    Gives the airmass for locations not at sea-level (i.e. not at standard
-    pressure). The input argument "AMrelative" is the relative airmass. The
-    input argument "pressure" is the pressure (in Pascals) at the location
-    of interest and must be greater than 0. The calculation for
-    absolute airmass is
-    
+    Gives the airmass for locations not at sea-level (i.e. not at
+    standard pressure). The input argument "AMrelative" is the relative
+    airmass. The input argument "pressure" is the pressure (in Pascals)
+    at the location of interest and must be greater than 0. The
+    calculation for absolute airmass is
+
     .. math::
         absolute airmass = (relative airmass)*pressure/101325
 
     Parameters
     ----------
 
-    airmass_relative : scalar or Series	
-        The airmass at sea-level. 
+    airmass_relative : scalar or Series
+        The airmass at sea-level.
 
     pressure : scalar or Series
-        The site pressure in Pascal. 
+        The site pressure in Pascal.
 
     Returns
     -------
@@ -131,9 +124,9 @@ def absoluteairmass(airmass_relative, pressure=101325.):
 
     References
     ----------
-    [1] C. Gueymard, "Critical analysis and performance assessment of 
-    clear sky solar irradiance models using theoretical and measured data,"
-    Solar Energy, vol. 51, pp. 121-138, 1993.
+    [1] C. Gueymard, "Critical analysis and performance assessment of
+    clear sky solar irradiance models using theoretical and measured
+    data," Solar Energy, vol. 51, pp. 121-138, 1993.
 
     '''
 
@@ -146,106 +139,106 @@ def relativeairmass(zenith, model='kastenyoung1989'):
     '''
     Gives the relative (not pressure-corrected) airmass.
 
-    Gives the airmass at sea-level when given a sun zenith angle
-    (in degrees). 
-    The ``model`` variable allows selection of different airmass models
-    (described below). If ``model`` is not 
-    included or is not valid, the default model is 'kastenyoung1989'.
+    Gives the airmass at sea-level when given a sun zenith angle (in
+    degrees). The ``model`` variable allows selection of different
+    airmass models (described below). If ``model`` is not included or is
+    not valid, the default model is 'kastenyoung1989'.
 
     Parameters
     ----------
 
-    zenith : float or Series 
-        Zenith angle of the sun in degrees.  
-        Note that some models use the apparent (refraction corrected)
-        zenith angle, and some models use the true
-        (not refraction-corrected) zenith angle.
-        See model descriptions to determine which type of zenith
-        angle is required.
-        Apparent zenith angles must be calculated at sea level.
-  
-    model : String 
+    zenith : float or Series
+        Zenith angle of the sun in degrees. Note that some models use
+        the apparent (refraction corrected) zenith angle, and some
+        models use the true (not refraction-corrected) zenith angle. See
+        model descriptions to determine which type of zenith angle is
+        required. Apparent zenith angles must be calculated at sea level.
+
+    model : String
         Available models include the following:
-        
+
         * 'simple' - secant(apparent zenith angle) -
           Note that this gives -inf at zenith=90
-        * 'kasten1966' - See reference [1] - requires apparent sun zenith
-        * 'youngirvine1967' - See reference [2] - requires true sun zenith
-        * 'kastenyoung1989' - See reference [3] - requires apparent sun zenith
-        * 'gueymard1993' - See reference [4] - requires apparent sun zenith
-        * 'young1994' - See reference [5] - requries true sun zenith
-        * 'pickering2002' - See reference [6] - requires apparent sun zenith
+        * 'kasten1966' - See reference [1] -
+          requires apparent sun zenith
+        * 'youngirvine1967' - See reference [2] -
+          requires true sun zenith
+        * 'kastenyoung1989' - See reference [3] -
+          requires apparent sun zenith
+        * 'gueymard1993' - See reference [4] -
+          requires apparent sun zenith
+        * 'young1994' - See reference [5] -
+          requries true sun zenith
+        * 'pickering2002' - See reference [6] -
+          requires apparent sun zenith
 
     Returns
     -------
-    airmass_relative : float or Series 
-        Relative airmass at sea level.  Will return NaN values for any 
+    airmass_relative : float or Series
+        Relative airmass at sea level.  Will return NaN values for any
         zenith angle greater than 90 degrees.
 
     References
     ----------
 
     [1] Fritz Kasten. "A New Table and Approximation Formula for the
-    Relative Optical Air Mass". Technical Report 136, Hanover, N.H.: U.S.
-    Army Material Command, CRREL.
+    Relative Optical Air Mass". Technical Report 136, Hanover, N.H.:
+    U.S. Army Material Command, CRREL.
 
-    [2] A. T. Young and W. M. Irvine, "Multicolor Photoelectric Photometry
-    of the Brighter Planets," The Astronomical Journal, vol. 72, 
-    pp. 945-950, 1967.
+    [2] A. T. Young and W. M. Irvine, "Multicolor Photoelectric
+    Photometry of the Brighter Planets," The Astronomical Journal, vol.
+    72, pp. 945-950, 1967.
 
-    [3] Fritz Kasten and Andrew Young. "Revised optical air mass tables and
-    approximation formula". Applied Optics 28:4735-4738
+    [3] Fritz Kasten and Andrew Young. "Revised optical air mass tables
+    and approximation formula". Applied Optics 28:4735-4738
 
-    [4] C. Gueymard, "Critical analysis and performance assessment of 
-    clear sky solar irradiance models using theoretical and measured data,"
-    Solar Energy, vol. 51, pp. 121-138, 1993.
+    [4] C. Gueymard, "Critical analysis and performance assessment of
+    clear sky solar irradiance models using theoretical and measured
+    data," Solar Energy, vol. 51, pp. 121-138, 1993.
 
-    [5] A. T. Young, "AIR-MASS AND REFRACTION," Applied Optics, vol. 33, 
+    [5] A. T. Young, "AIR-MASS AND REFRACTION," Applied Optics, vol. 33,
     pp. 1108-1110, Feb 1994.
 
     [6] Keith A. Pickering. "The Ancient Star Catalog". DIO 12:1, 20,
-    
-    [7] Matthew J. Reno, Clifford W. Hansen and Joshua S. Stein,
-    "Global Horizontal Irradiance Clear Sky Models: Implementation and Analysis"
+
+    [7] Matthew J. Reno, Clifford W. Hansen and Joshua S. Stein, "Global
+    Horizontal Irradiance Clear Sky Models: Implementation and Analysis"
     Sandia Report, (2012).
     '''
-    
+
     z = zenith
     zenith_rad = np.radians(z)
-    
+
     model = model.lower()
-    
+
     if 'kastenyoung1989' == model:
-        AM = ( 1.0 / (np.cos(zenith_rad) +
-            0.50572*(((6.07995 + (90 - z)) ** - 1.6364))) )
+        am = (1.0 / (np.cos(zenith_rad) +
+              0.50572*(((6.07995 + (90 - z)) ** - 1.6364))))
     elif 'kasten1966' == model:
-        AM = 1.0 / (np.cos(zenith_rad) + 0.15*((93.885 - z) ** - 1.253))
+        am = 1.0 / (np.cos(zenith_rad) + 0.15*((93.885 - z) ** - 1.253))
     elif 'simple' == model:
-        AM = 1.0 / np.cos(zenith_rad)
+        am = 1.0 / np.cos(zenith_rad)
     elif 'pickering2002' == model:
-        AM = ( 1.0 / (np.sin(np.radians(90 - z +
-            244.0 / (165 + 47.0 * (90 - z) ** 1.1)))) )
+        am = (1.0 / (np.sin(np.radians(90 - z +
+              244.0 / (165 + 47.0 * (90 - z) ** 1.1)))))
     elif 'youngirvine1967' == model:
-        AM = ( (1.0 / np.cos(zenith_rad)) *
-            (1 - 0.0012*( (1.0 / np.cos(zenith_rad)) ** 2) - 1) )
+        am = ((1.0 / np.cos(zenith_rad)) *
+              (1 - 0.0012*((1.0 / np.cos(zenith_rad)) ** 2) - 1))
     elif 'young1994' == model:
-        AM = ( (1.002432*((np.cos(zenith_rad)) ** 2) +
-            0.148386*(np.cos(zenith_rad)) + 0.0096467) /
-            (np.cos(zenith_rad) ** 3 +
-            0.149864*(np.cos(zenith_rad) ** 2) +
-            0.0102963*(np.cos(zenith_rad)) + 0.000303978) )
+        am = ((1.002432*((np.cos(zenith_rad)) ** 2) +
+              0.148386*(np.cos(zenith_rad)) + 0.0096467) /
+              (np.cos(zenith_rad) ** 3 +
+              0.149864*(np.cos(zenith_rad) ** 2) +
+              0.0102963*(np.cos(zenith_rad)) + 0.000303978))
     elif 'gueymard1993' == model:
-        AM = ( 1.0 / (np.cos(zenith_rad) +
-            0.00176759*(z)*((94.37515 - z) ** - 1.21563)) )
+        am = (1.0 / (np.cos(zenith_rad) +
+              0.00176759*(z)*((94.37515 - z) ** - 1.21563)))
     else:
-        pvl_logger.warning("%s is not a valid model type for relative airmass. The 'kastenyoung1989' model was used.",
-                           model)
-        AM = ( 1.0 / (np.cos(zenith_rad) +
-            0.50572*(((6.07995 + (90 - z)) ** - 1.6364))) )
-    
+        raise ValueError('%s is not a valid model for relativeairmass', model)
+
     try:
-        AM[z > 90] = np.nan
+        am[z > 90] = np.nan
     except TypeError:
-        AM = np.nan if z > 90 else AM
-        
-    return AM
+        am = np.nan if z > 90 else am
+
+    return am

pvlib/test/test_atmosphere.py

@@ -15,7 +15,7 @@
 
 
 # setup times and location to be tested.
-times = pd.date_range(start=datetime.datetime(2014,6,24), 
+times = pd.date_range(start=datetime.datetime(2014,6,24),
                       end=datetime.datetime(2014,6,26), freq='1Min')
 
 tus = Location(32.2, -111, 'US/Arizona', 700)
@@ -30,23 +30,28 @@
 
 def test_pres2alt():
     atmosphere.pres2alt(100000)
-    
+
 def test_alt2press():
     atmosphere.pres2alt(1000)
 
 
 # two functions combined will generate unique unit tests for each model
 def test_airmasses():
     models = ['simple', 'kasten1966', 'youngirvine1967', 'kastenyoung1989',
-              'gueymard1993', 'young1994', 'pickering2002', 'invalid']
+              'gueymard1993', 'young1994', 'pickering2002']
     for model in models:
         yield run_airmass, model, ephem_data['zenith']
 
 
 def run_airmass(model, zenith):
     atmosphere.relativeairmass(zenith, model)
 
-    
+
+@raises(ValueError)
+def test_airmass_invalid():
+    atmosphere.relativeairmass(ephem_data['zenith'], 'invalid')
+
+
 def test_absoluteairmass():
     relative_am = atmosphere.relativeairmass(ephem_data['zenith'], 'simple')
     atmosphere.absoluteairmass(relative_am)