NF: Re-enable min_n_entropy stimulus selection

Closes GH-12.

questplus/qp.py

@@ -62,9 +62,11 @@ def __init__(self, *,
 
         stim_selection_options
             Use this argument to specify options for the stimulus selection
-            method specified via `stim_selection_method`. Currently, this is
-            only used to specify the number of `n` stimuli that will yield the
-            `n` smallest entropies `stim_selection_method=min_n_entropy`.
+            method specified via `stim_selection_method`. Currently, this can
+            be used to specify the number of `n` stimuli that will yield the
+            `n` smallest entropies if `stim_selection_method=min_n_entropy`,
+            and`max_consecutive_reps`, the number of times the same stimulus
+            can be presented consecutively.
 
         param_estimation_method
             The method to use when deriving the final parameter estimate.
@@ -84,7 +86,12 @@ def __init__(self, *,
         self.likelihoods = self._gen_likelihoods()
 
         self.stim_selection = stim_selection_method
-        self.stim_selection_options = stim_selection_options
+
+        if (self.stim_selection == 'min_n_entropy' and
+                stim_selection_options is None):
+            self.stim_selection_options = dict(n=4, max_consecutive_reps=2)
+        else:
+            self.stim_selection_options = stim_selection_options
 
         self.param_estimation_method = param_estimation_method
 
@@ -199,7 +206,6 @@ def next_stim(self) -> dict:
         The stimulus to present next.
 
         """
-        stim_selection = self.stim_selection
         new_posterior = self.posterior * self.likelihoods
 
         # Probability.
@@ -215,31 +221,39 @@ def next_stim(self) -> dict:
         # Expected entropies for all possible stimulus parameters.
         EH = (pk * H).sum(dim=list(self.outcome_domain.keys()))
 
-        if stim_selection == 'min_entropy':
+        if self.stim_selection == 'min_entropy':
             # Get coordinates of stimulus properties that minimize entropy.
             index = np.unravel_index(EH.argmin(), EH.shape)
             coords = EH[index].coords
             stim = {stim_property: stim_val.item()
                     for stim_property, stim_val in coords.items()}
             self.entropy = EH.min().item()
-        # FIXME: currently disabled, need to adopt above method for
-        # finding correct coordinates!
-        # elif stim_selection == 'min_n_entropy':
-        #     index = np.argsort(EH)[:4]
-        #     while True:
-        #         stim_candidates = self.stim_domain['intensity'][index.values]
-        #         stim = np.random.choice(stim_candidates)
-        #
-        #         if len(self.stim_history['intensity']) < 2:
-        #             break
-        #         elif (np.isclose(stim, self.stim_history['intensity'][-1]) and
-        #               np.isclose(stim, self.stim_history['intensity'][-2])):
-        #             print('\n  ==> shuffling again... <==\n')
-        #             continue
-        #         else:
-        #             break
-        #
-        #     print(f'options: {self.stim_domain["intensity"][index.values]} -> {stim}')
+        elif self.stim_selection == 'min_n_entropy':
+            # Number of stimuli to include (the n stimuli that yield the lowest
+            # entropies)
+            n_stim = self.stim_selection_options['n']
+
+            indices = np.unravel_index(EH.argsort(), EH.shape)[0]
+            indices = indices[:n_stim]
+
+            while True:
+                # Randomly pick one index and retrieve its coordinates
+                # (stimulus parameters).
+                candidate_index = np.random.choice(indices)
+                coords = EH[candidate_index].coords
+                stim = {stim_property: stim_val.item()
+                        for stim_property, stim_val in coords.items()}
+
+                max_reps = self.stim_selection_options['max_consecutive_reps']
+
+                if len(self.stim_history) < 2:
+                    break
+                elif all([stim == prev_stim
+                          for prev_stim in self.stim_history[-max_reps:]]):
+                    # Shuffle again.
+                    continue
+                else:
+                    break
         else:
             raise ValueError('Unknown stim_selection supplied.')