function reconstruct_signal_hess

diffpy/snmf/subroutines.py

@@ -206,7 +206,31 @@ def reconstruct_signal(components, signal_idx):
         reconstruction += stretched_and_weighted
     return reconstruction
 
+def reconstruct_signal_hess(components, signal_idx):
+    """Reconstruct a specific signal's hessian (second derivative) from its weighted and stretched components.
 
+    Calculates the linear combination of stretched components' hessians where each term is a stretched component's
+    hessian mulitplied by its weight factor.
+
+    Parameters
+    ----------
+    components: tuple of ComponentSignal objects
+      The tuple containing the ComponentSignal objects
+    signal_idx: int
+      The index of the specific signal in the input data to be reconstructed.
+
+    Returns
+    -------
+    1d array like
+      The reconstruction of a signal's hessian from calculated weights, stretching factors, and iq values
+    """
+    signal_length = len(components[0].grid)
+    reconstruction = np.zeros(signal_length)
+    for component in components:
+        stretched = component.apply_stretch(signal_idx)[2]
+        stretched_and_weighted = component.apply_weight(signal_idx, stretched)
+        reconstruction += stretched_and_weighted
+    return reconstruction
 def initialize_arrays(number_of_components, number_of_moments, signal_length):
     """Generates the initial guesses for the weight, stretching, and component matrices
 

diffpy/snmf/tests/test_subroutines.py

@@ -3,7 +3,7 @@
 from diffpy.snmf.containers import ComponentSignal
 from diffpy.snmf.subroutines import objective_function, get_stretched_component, reconstruct_data, get_residual_matrix, \
     update_weights_matrix, initialize_arrays, lift_data, initialize_components, construct_stretching_matrix, \
-    construct_component_matrix, construct_weight_matrix, update_weights, reconstruct_signal
+    construct_component_matrix, construct_weight_matrix, update_weights, reconstruct_signal, reconstruct_signal_hess
 
 to = [
     ([[[1, 2], [3, 4]], [[5, 6], [7, 8]], 1e11, [[1, 2], [3, 4]], [[1, 2], [3, 4]], 1], 2.574e14),
@@ -251,3 +251,17 @@ def test_update_weights(tuw):
 def test_reconstruct_signal(trs):
     actual = reconstruct_signal(trs[0], trs[1])
     assert len(actual) == len(trs[0][0].grid)
+
+trsh = [([ComponentSignal([0, .25, .5, .75, 1], 2, 0), ComponentSignal([0, .25, .5, .75, 1], 2, 1),
+         ComponentSignal([0, .25, .5, .75, 1], 2, 2)], 1),
+       ([ComponentSignal([0, .25, .5, .75, 1], 2, 0), ComponentSignal([0, .25, .5, .75, 1], 2, 1),
+         ComponentSignal([0, .25, .5, .75, 1], 2, 2)], 0),
+       ([ComponentSignal([0, .25, .5, .75, 1], 3, 0), ComponentSignal([0, .25, .5, .75, 1], 3, 1),
+         ComponentSignal([0, .25, .5, .75, 1], 3, 2)], 2),
+       # ([ComponentSignal([0, .25, .5, .75, 1], 2, 0), ComponentSignal([0, .25, .5, .75, 1], 2, 1),
+        # ComponentSignal([0, .25, .5, .75, 1], 2, 2)], -1),
+]
+@pytest.mark.parametrize('trsh', trsh)
+def test_reconstruct_signal_hess(trsh):
+    actual = reconstruct_signal(trsh[0], trsh[1])
+    assert len(actual) == len(trsh[0][0].grid)