Fixes for issue 65 with nan elements for d0 calculation (josephhardin…

…ee#88)

* This adds some error catching code for cases where D0 is being calculated with arrays that contain nans, or single elements that are above zero. Also some more unit tests are added to stop regression of this in the future.

.travis.yml

@@ -43,11 +43,12 @@ matrix:
 #      python: "3.7-dev"
 before_install:
 - pip install pytest pytest-cov
+- pip install coverage==4.5.4 
 - pip install coveralls
 install: source continuous_integration/install.sh
 script: eval xvfb-run python -m pytest $PYTEST_ARGS
 #script: eval xvfb-run nosetests $NOSE_ARGS
 after_success:
-- coveralls
+# - coveralls
 - if [[ "$DOC_BUILD" == "true" ]]; then cd $TRAVIS_BUILD_DIR; source continuous_integration/build_docs.sh;
   fi

continuous_integration/install.sh

@@ -44,7 +44,8 @@ fi
 
 # install coverage modules
 if [[ "$COVERALLS" == "true" ]]; then
-    pip install python-coveralls
+    pip install 'coverage<5.0'
+    pip install coveralls
 fi
 
 pip install -e .

pydsd/DropSizeDistribution.py

@@ -399,10 +399,17 @@ def _calculate_D0(self, N):
         rho_w = 1e-3
         W_const = rho_w * np.pi / 6.0
 
-        if np.sum(N) == 0:
+        if np.nansum(N) == 0:
             return 0
 
-        cum_W = W_const * np.cumsum(
+        if (
+            np.count_nonzero(N[np.isfinite(N)]) == 1
+        ):  # If there is only one nonzero/nan element, return that diameter.
+            return self.diameter["data"][
+                np.nanargmax(N)
+            ]  # This gets around weirdness with only one valid point.
+
+        cum_W = W_const * np.nancumsum(
             [
                 N[k] * self.spread["data"][k] * (self.diameter["data"][k] ** 3)
                 for k in range(0, len(N))

pydsd/tests/test_DropSizeDistribution.py

@@ -1,5 +1,6 @@
 import pytest
 import os.path
+import numpy as np
 
 from ..aux_readers import ARM_Vdis_Reader
 from ..io.NetCDFWriter import write_netcdf
@@ -30,3 +31,22 @@ def test_changing_canting_angle_updates_value(self, two_dvd_open_test_file):
 
     def test_canting_angle_has_default_value(self, two_dvd_open_test_file):
         assert "canting_angle" in two_dvd_open_test_file.scattering_params.keys()
+
+    def test_calculating_D0_with_nan_actually_works(self, two_dvd_open_test_file):
+        two_dvd_open_test_file.fields["Nd"]["data"][0, 0] = np.nan  # Force a nan error
+        two_dvd_open_test_file.fields["Nd"]["data"][0, 1] = 5
+
+        two_dvd_open_test_file.calculate_dsd_parameterization()
+        assert two_dvd_open_test_file.fields["D0"]["data"][0] != np.nan
+        assert (
+            two_dvd_open_test_file.fields["D0"]["data"][0]
+            == two_dvd_open_test_file.diameter["data"][1]
+        )
+
+    def test_calculating_D0_returns_correct_values(self, two_dvd_open_test_file):
+        two_dvd_open_test_file.fields["Nd"]["data"][0, 0] = 1  # Force a nan error
+        two_dvd_open_test_file.fields["Nd"]["data"][0, 1] = 2
+        two_dvd_open_test_file.calculate_dsd_parameterization()
+        assert np.isclose(
+            two_dvd_open_test_file.fields["D0"]["data"][0], .198, rtol=.01
+        )  # One percent tolerance is closer than my hand calcs.