removes unused pressure arg from Irradiance.liujordan function (#389)

* fix for issue #343

Now, passed 'offset' parameter are used instead of it's default value.

* test for issue #343

* solar_position_method passed to basic_chain wasn't used causing
execution of solarposition.get_solarposition with default 'nrel_numpy'
value in all cases.

* Update modelchain.py

doc string fixes for modelchain.basic_chain function

* Update v0.5.1.rst

* Update v0.5.1.rst

* Update v0.5.1.rst

* Update v0.5.1.rst

* Update v0.5.1.rst

* fix for issue #386

* what's new for issue #386

* test update for issue #386

* Update conftest.py

* Update test_irradiance.py

* Update v0.5.2.rst

* Update v0.5.2.rst

Author: KonstantinTr

docs/sphinx/source/whatsnew/v0.5.2.rst

@@ -5,7 +5,7 @@ v0.5.2 (__, 2017)
 
 API Changes
 ~~~~~~~~~~~
-*
+* removed unused 'pressure' arg from irradiance.liujordan function (:issue:`386`)
 
 Enhancements
 ~~~~~~~~~~~~

pvlib/irradiance.py

@@ -1489,8 +1489,7 @@ def erbs(ghi, zenith, doy):
     return data
 
 
-def liujordan(zenith, transmittance, airmass, pressure=101325.,
-              dni_extra=1367.0):
+def liujordan(zenith, transmittance, airmass, dni_extra=1367.0):
     '''
     Determine DNI, DHI, GHI from extraterrestrial flux, transmittance,
     and optical air mass number.
@@ -1531,10 +1530,10 @@ def liujordan(zenith, transmittance, airmass, pressure=101325.,
     radiation".  Solar Energy 4:1-19
     '''
 
-    tao = transmittance
+    tau = transmittance
 
-    dni = dni_extra*tao**airmass
-    dhi = 0.3 * (1.0 - tao**airmass) * dni_extra * np.cos(np.radians(zenith))
+    dni = dni_extra*tau**airmass
+    dhi = 0.3 * (1.0 - tau**airmass) * dni_extra * np.cos(np.radians(zenith))
     ghi = dhi + dni * np.cos(np.radians(zenith))
 
     irrads = OrderedDict()

pvlib/test/test_irradiance.py

@@ -201,8 +201,7 @@ def test_liujordan():
         columns=['ghi', 'dni', 'dhi'],
         index=[0])
     out = irradiance.liujordan(
-        pd.Series([10]), pd.Series([0.5]), pd.Series([1.1]),
-        pressure=93000., dni_extra=1400)
+        pd.Series([10]), pd.Series([0.5]), pd.Series([1.1]), dni_extra=1400)
     assert_frame_equal(out, expected)