add r_v kwarg to fitzpatrick99()

docs/index.rst

@@ -61,33 +61,28 @@ Get extinction in magnitudes at a set of wavelengths for various dust laws::
   >>> extinction.odonnell94(wave, 1.0, 3.1)
   array([ 2.84252644,  1.42617802,  0.60793495])
 
+  # Fitzpatrick (1999)
+  >>> extinction.fitzpatrick99(wave, 1.0, 3.1)
+  array([ 2.76225609,  1.79674653,  1.42325373])
 
-The Fitzpatrick (1999) and Fitzpatrick & Massa (2007) functions have fixed
-:math:`R_V` of 3.1::
-        
-   # Fitzpatrick (1999) for fixed R_V = 3.1
-   >>> extinction.fitzpatrick99(wave, 1.0)
-   array([ 2.76225609,  1.42338583,  0.55346406])
+
+The Fitzpatrick & Massa (2007) function has a fixed :math:`R_V` of 3.1::
 
    >>> extinction.fm07(wave, 1.0)
    array([ 2.90478329,  1.42645161,  0.54703201])
    
-   # Fitzpatrick (1999) can also be used with other R_V values.
-   # First, construct a function for a given R_V value (note capital "F"):
-   >>> f = extinction.Fitzpatrick99(2.1)
-
-   # Then, call the function:
-   >>> f(wave, 1.0)
-   array([ 4.28908428,  1.6266948 ,  0.47992809])
-
 All extinction laws accept a ``unit`` keyword to change the interpretation of
 the wavelength array from Angstroms to inverse microns::
 
   >>> wave = np.array([5., 2.5, 1.25])  # wavelength in inverse microns
 
   >>> extinction.ccm89(wave, 1.0, 3.1, unit='invum')
   array([ 2.84252644,  1.4645557 ,  0.59748901])  # extinction in magnitudes
-   
+
+
+Redden or deredden
+..................
+
 To "redden" or "deredden" flux values by some amount, use the
 ``apply`` convenience function::
 

extinction.pyx

@@ -447,10 +447,10 @@ cdef class Fitzpatrick99(object):
 _fitzpatrick99_fixed = Fitzpatrick99(3.1)
 
 
-def fitzpatrick99(wave, a_v, unit='aa'):
-    """fitzpatrick99(wave, a_v, unit='aa')
+def fitzpatrick99(wave, a_v, r_v=3.1, unit='aa'):
+    """fitzpatrick99(wave, a_v, r_v=3.1, unit='aa')
 
-    Fitzpatrick (1999) dust extinction function for R_V = 3.1.
+    Fitzpatrick (1999) dust extinction function.
 
     Fitzpatrick (1999) [1]_ model which relies on the parametrization
     of Fitzpatrick & Massa (1990) [2]_ in the UV (below 2700 A) and
@@ -467,6 +467,8 @@ def fitzpatrick99(wave, a_v, unit='aa'):
         Input wavelengths or wavenumbers (see units).
     a_v : float
         Total V-band extinction in magnitudes.
+    r_v : float
+        Ratio of total to selective extinction, A_V / E(B-V).
     unit : {'aa', 'invum'}, optional
         Wavelength units: Angstroms or inverse microns.
 
@@ -479,8 +481,10 @@ def fitzpatrick99(wave, a_v, unit='aa'):
     .. [1] Fitzpatrick, E. L. 1999, PASP, 111, 63
     .. [2] Fitzpatrick, E. L. & Massa, D. 1990, ApJS, 72, 163
     """
-    return _fitzpatrick99_fixed(wave, a_v, unit=unit)
-
+    if r_v == 3.1:
+        return _fitzpatrick99_fixed(wave, a_v, unit=unit)
+    else:
+        return Fitzpatrick99(r_v)(wave, a_v, unit=unit)
 
 # -----------------------------------------------------------------------------
 # Fitzpatrick & Massa 2007

setup.py

@@ -28,7 +28,7 @@
 version = re.findall(r"__version__ = \"(.*?)\"", open(fname).read())[0]
 
 classifiers = [
-    "Development Status :: 3 - Alpha",
+    "Development Status :: 4 - Beta",
     "Programming Language :: Python :: 2",
     "Programming Language :: Python :: 3",
     "License :: OSI Approved :: MIT License",

test.py

@@ -151,6 +151,15 @@ def test_fitzpatrick99_r_v():
     assert f.r_v == 2.1
 
 
+def test_fitzpatrick99_func():
+    """Check passing R_V."""
+
+    wave = np.array([2000., 30000.])
+    for r_v in (3.1, 4.0):
+        assert np.all(extinction.Fitzpatrick99(r_v)(wave, 1.0) ==
+                      extinction.fitzpatrick99(wave, 1.0, r_v))
+
+
 def test_fm07():
     wave = np.arange(3000., 9000., 1000)