Refs #39. forcing correct energy axis in getdos and warn. added a tes…

…t case

multiphonon/getdos.py

@@ -27,6 +27,7 @@ def getDOS(sample_nxs, mt_nxs=None, mt_fraction=0.9, const_bg_fraction=0.,
         iqe_h5 = os.path.abspath(os.path.join(workdir, iqe_h5))
     # reduce
     Eaxis = _normalize_axis_setting(Emin, Emax, dE)
+    Eaxis = _checkEaxis(*Eaxis)
     Qaxis = _normalize_axis_setting(Qmin, Qmax, dQ)
     yield "Convert sample data to powder I(Q,E)"
     raw2iqe(sample_nxs, iqe_nxs, iqe_h5, Eaxis, Qaxis)
@@ -46,7 +47,7 @@ def getDOS(sample_nxs, mt_nxs=None, mt_fraction=0.9, const_bg_fraction=0.,
     # interpolate data
     from .sqe import interp
     # probably don't need this line
-    newiqe = interp(iqehist, newE = np.arange(Emin, Emax, dE))
+    newiqe = interp(iqehist, newE = np.arange(*Eaxis))
     # save interpolated data
     hh.dump(newiqe, 'iqe-interped.h5')
     # init dos
@@ -68,6 +69,22 @@ def getDOS(sample_nxs, mt_nxs=None, mt_fraction=0.9, const_bg_fraction=0.,
     return
 
 
+def _checkEaxis(Emin, Emax, dE):
+    saved = Emin, Emax, dE
+    centers = np.arange(Emin, Emax, dE)
+    if np.isclose(centers, 0.).any():
+        return saved
+    import warnings
+    Emin = int(Emin/dE) * dE
+    Emax = int(Emax/dE) * dE
+    new = Emin, Emax, dE
+    warnings.warn(
+        "Zero has to be one of the ticks in the energy axis.\n"
+        "Energy axis modified from %s to %s \n" % (saved, new)
+        )
+    return new
+
+
 def _normalize_axis_setting(min, max, delta):
     # try to deal with numerical error
     nsteps = round( 1.*(max-min)/delta )

tests/getdos_TestCase.py

@@ -9,18 +9,29 @@
 import os
 datadir = os.path.join(os.path.dirname(__file__), "data")
 
+from multiphonon.getdos import getDOS
+
 import unittest
 class TestCase(unittest.TestCase):
 
     def test1(self):
         "multiphonon.getdos"
-        from multiphonon.getdos import getDOS
         list(getDOS(os.path.join(datadir, "ARCS_V_annulus.nxs")))
         return
 
+    def test1a(self):
+        "multiphonon.getdos: check energy axis"
+        import warnings
+        with warnings.catch_warnings(record=True) as w:
+            warnings.simplefilter('always')
+            for  _ in getDOS(os.path.join(datadir, "ARCS_V_annulus.nxs"), Emin=-50.5, Emax=80, dE=1.):
+                assert len(w)==1
+                assert "Energy axis modified" in str(w[-1].message)
+                break
+        return
+
     def test2(self):
         "multiphonon.getdos: MT can"
-        from multiphonon.getdos import getDOS
         list(getDOS(
             os.path.join(datadir, "ARCS_V_annulus.nxs"),
             mt_nxs = os.path.join(datadir, "ARCS_V_annulus.nxs"),
@@ -30,7 +41,6 @@ def test2(self):
 
     def test3(self):
         "multiphonon.getdos: low T"
-        from multiphonon.getdos import getDOS
         list(getDOS(os.path.join(datadir, "ARCS_V_annulus.nxs"), T=1.5))
         return