Merge pull request #12 from karllark/generic_ext

Extinguish function to class
Travis build failing due to scipy docs being offline.  All other builds working.

dust_extinction/dust_extinction.py

@@ -33,7 +33,7 @@ class CCM89(Model):
 
     Returns
     -------
-    elvebv: float
+    elvebv: np.array(dtype=float)
         E(x-V)/E(B-V) extinction curve [mag]
 
     Raises
@@ -50,8 +50,6 @@ class CCM89(Model):
     F99 should be used instead as it is based on 10x more observations 
     and a better treatment of the optical/NIR photometry based portion 
     of the curves.
-
-    CCM89 is mainly for historical puposes
     """
     inputs = ('x',)
     outputs = ('elvebv',)
@@ -146,6 +144,47 @@ def evaluate(in_x, Rv):
         a[fuv_indxs] = np.polyval((-.070, .137, -.628, -1.073), y)
         b[fuv_indxs] = np.polyval((.374, -.42, 4.257, 13.67), y)
 
-        # return Al/Av
+        # return E(lambda-V)/E(B-V)
         return a + b/Rv
+
+    def extinguish(self, x, Av=None, Ebv=None):
+        """
+        Calculate the extinction as a fraction
+
+        Parameters
+        ----------
+        x: float
+           expects either x in units of wavelengths or frequency
+           or assumes wavelengths in wavenumbers [1/micron]
+           internally wavenumbers are used
+
+        Av: float
+           A(V) value of dust column
+           Av or Ebv must be set
+
+        Ebv: float
+           E(B-V) value of dust column
+           Av or Ebv must be set
+
+        Returns
+        -------
+        frac_ext: np.array(dtype=float)
+           extinction as a function of x 
+        """
+        # get the extinction curve
+        elvebv = self(x)
+
+        # check that av or ebv is set
+        if (Av is None) and (Ebv is None):
+            raise InputParameterError('neither Av or Ebv passed, one required')
+
+        # if Av is not set and Ebv set, convert to Av
+        if Av is None:
+            Av = self.Rv*Ebv
+
+        # convert to A(lambda)/A(V)
+        alav = elvebv/self.Rv + 1
+
+        # return fractional extinction
+        return np.power(10.0,-0.4*alav*Av)
 

dust_extinction/tests/coveragerc

@@ -10,6 +10,9 @@ omit =
    {packagename}/tests/*
    {packagename}/*/tests/*
    {packagename}/*/*/tests/*
+   {packagename}/plots/*
+   {packagename}/*/plots/*
+   {packagename}/*/*/plots/*
    {packagename}/version*
 
 [report]
@@ -28,4 +31,4 @@ exclude_lines =
    def main\(.*\):
 
    # Ignore branches that don't pertain to this version of Python
-   pragma: py{ignore_python_version}
+   pragma: py{ignore_python_version}

dust_extinction/tests/test_ccm89.py

@@ -62,9 +62,8 @@ def test_invalid_micron(x_invalid_angstrom):
                                 +  ' <= x <= ' \
                                 + str(tmodel.x_range[1]) \
                                 + ', x has units 1/micron]'
-
-@pytest.mark.parametrize("Rv", [2.0, 3.0, 3.1, 4.0, 5.0, 6.0])
-def test_extinction_CCM89_values(Rv):
+
+def get_elvebv_cor_vals(Rv):
     # testing wavenumbers
     x = np.array([ 10.  ,   9.  ,   8.  ,   7.  ,
                    6.  ,   5.  ,   4.6 ,   4.  ,
@@ -115,9 +114,54 @@ def test_extinction_CCM89_values(Rv):
     else:
         cor_vals = np.array([ 0.0 ])
 
+    return (x, cor_vals)
+
+
+@pytest.mark.parametrize("Rv", [2.0, 3.0, 3.1, 4.0, 5.0, 6.0])
+def test_extinction_CCM89_values(Rv):
+    # get the correct values
+    x, cor_vals = get_elvebv_cor_vals(Rv)
+
     # initialize extinction model    
     tmodel = CCM89(Rv=Rv)
 
     # test
     np.testing.assert_allclose(tmodel(x), cor_vals)
+
+def test_extinguish_no_av_or_ebv():
+    tmodel = CCM89()
+    with pytest.raises(InputParameterError) as exc:
+        tmodel.extinguish([1.0])
+    assert exc.value.args[0] == 'neither Av or Ebv passed, one required'
+
+@pytest.mark.parametrize("Rv", [2.0, 3.0, 3.1, 4.0, 5.0, 6.0])
+def test_extinction_CCM89_extinguish_values_Av(Rv):
+    # get the correct values
+    x, cor_vals = get_elvebv_cor_vals(Rv)
+
+    # calculate the cor_vals in fractional units
+    Av = 1.0
+    cor_vals = np.power(10.0,-0.4*(cor_vals/Rv+1)*Av)
+
+    # initialize extinction model    
+    tmodel = CCM89(Rv=Rv)
+
+    # test
+    np.testing.assert_allclose(tmodel.extinguish(x, Av=Av), cor_vals)
+
+@pytest.mark.parametrize("Rv", [2.0, 3.0, 3.1, 4.0, 5.0, 6.0])
+def test_extinction_CCM89_extinguish_values_Ebv(Rv):
+    # get the correct values
+    x, cor_vals = get_elvebv_cor_vals(Rv)
+
+    # calculate the cor_vals in fractional units
+    Ebv = 1.0
+    Av = Ebv*Rv
+    cor_vals = np.power(10.0,-0.4*(cor_vals/Rv+1)*Av)
+
+    # initialize extinction model    
+    tmodel = CCM89(Rv=Rv)
+
+    # test
+    np.testing.assert_allclose(tmodel.extinguish(x, Ebv=Ebv), cor_vals)