Merge branch '536-plot_waveform_posterior-uses-non-representative-samples' into 'master'

Resolve "plot_waveform_posterior uses non representative samples"

Closes #536

See merge request !894

bilby/gw/result.py

@@ -337,7 +337,7 @@ class CompactBinaryCoalescenceResult(CoreResult):
             interferometer.name))
 
         if n_samples is None:
-            n_samples = len(self.posterior)
+            samples = self.posterior
         elif n_samples > len(self.posterior):
             logger.debug(
                 "Requested more waveform samples ({}) than we have "
@@ -345,14 +345,16 @@ class CompactBinaryCoalescenceResult(CoreResult):
                     n_samples, len(self.posterior)
                 )
             )
-            n_samples = len(self.posterior)
+            samples = self.posterior
+        else:
+            samples = self.posterior.sample(n_samples, replace=False)
 
         if start_time is None:
             start_time = - 0.4
-        start_time = np.mean(self.posterior.geocent_time) + start_time
+        start_time = np.mean(samples.geocent_time) + start_time
         if end_time is None:
             end_time = 0.2
-        end_time = np.mean(self.posterior.geocent_time) + end_time
+        end_time = np.mean(samples.geocent_time) + end_time
         if format == "html":
             start_time = - np.inf
             end_time = np.inf
@@ -470,8 +472,8 @@ class CompactBinaryCoalescenceResult(CoreResult):
 
         fd_waveforms = list()
         td_waveforms = list()
-        for ii in range(n_samples):
-            params = dict(self.posterior.iloc[ii])
+        for _, params in samples.iterrows():
+            params = dict(params)
             wf_pols = waveform_generator.frequency_domain_strain(params)
             fd_waveform = interferometer.get_detector_response(wf_pols, params)
             fd_waveforms.append(fd_waveform[frequency_idxs])