Fix npred cube tutorial

docs/tutorials/npred/npred_general.py

@@ -24,7 +24,7 @@ def prepare_images():
     exposure_cube.data = Quantity(exposure_cube.data.value, 'cm2 s')
 
     # Re-project background cube
-    repro_bg_cube = background_model.reproject_to(exposure_cube)
+    repro_bg_cube = background_model.reproject(exposure_cube)
 
     # Define energy band required for output
     energies = EnergyBounds([10, 500], 'GeV')
@@ -38,12 +38,8 @@ def prepare_images():
                                          offset_max=Angle(3, 'deg'))
 
     # Counts data
-    counts_data = fits.open(counts_file)[0].data
-    counts_wcs = WCS(fits.open(counts_file)[0].header)
-    counts_cube = SkyCube(data=Quantity(counts_data, ''),
-                          wcs=counts_wcs,
-                          energy=energies)
-    counts_cube = counts_cube.reproject_to(npred_cube, projection_type='nearest-neighbor')
+    counts_cube = SkyCube.read(counts_file, format='fermi-counts')
+    counts_cube = counts_cube.reproject(npred_cube)
 
     counts = counts_cube.data[0]
     model = convolved_npred_cube.data[0]

gammapy/cube/core.py

@@ -358,7 +358,7 @@ def spectral(self):
         data = np.nansum(np.nansum(self.data, axis=1), axis=1)
         return CountsSpectrum(data=data, energy=self.energy)
 
-    def lookup(self, position, energy, interpolation=None):
+    def lookup(self, position, energy, interpolation=False):
         """Differential flux.
 
         Parameters
@@ -379,8 +379,14 @@ def lookup(self, position, energy, interpolation=None):
 
         z, y, x = self.wcs_skycoord_to_pixel(position, energy)
 
-        return self.data[np.rint(z).astype('int'), np.rint(y).astype('int'),
-                         np.rint(x).astype('int')]
+        if interpolation:
+            shape = z.shape
+            pix_coords = np.column_stack([x.flat, y.flat, z.flat])
+            vals = self._interpolate(pix_coords)
+            return vals.reshape(shape)
+        else:
+            return self.data[np.rint(z).astype('int'), np.rint(y).astype('int'),
+                             np.rint(x).astype('int')]
 
     def show(self, viewer='mpl', ds9options=None, **kwargs):
         """

gammapy/cube/utils.py

@@ -45,19 +45,17 @@ def compute_npred_cube(flux_cube, exposure_cube, energy_bins,
 
     energy_centers = energy_bins.log_centers
     wcs = exposure_cube.wcs
-    coordinates = exposure_cube.coordinates()
-    lon = coordinates.data.lon
-    lat = coordinates.data.lat
+    coordinates = exposure_cube.spatial.coordinates()
+    solid_angle = exposure_cube.spatial.solid_angle()
 
-    solid_angle = exposure_cube.solid_angle
     npred_cube = np.zeros((len(energy_bins) - 1,
                            exposure_cube.data.shape[1], exposure_cube.data.shape[2]))
     for i in range(len(energy_bins) - 1):
         energy_bound = energy_bins[i:i + 2]
         int_flux = flux_cube.integral_flux_image(energy_bound, integral_resolution)
         int_flux = Quantity(int_flux.data, '1 / (cm2 s sr)')
-        exposure = Quantity(exposure_cube.flux(lon, lat,
-                                               energy_centers[i]).value, 'cm2 s')
+        energy = energy_centers[i] * np.ones(coordinates.shape)
+        exposure = Quantity(exposure_cube.lookup(coordinates, energy, interpolation=True), 'cm2 s')
         npred_image = int_flux * exposure * solid_angle
         npred_cube[i] = npred_image.to('')
     npred_cube = np.nan_to_num(npred_cube)