Plot function bugs fixed

AUTHORS.md

@@ -252,7 +252,8 @@
 - Osman Zubair <https://github.com/okz12>
 - Viresh Gupta <https://github.com/virresh>
 - Ondřej Cífka <https://github.com/cifkao>
-- Iris X. Zhou <https://github.com/irisxzhou> 
+- Iris X. Zhou <https://github.com/irisxzhou>
+- Devashish Lal <https://github.com/BLaZeKiLL>
 
 
 ## Others whose work we've taken and included in NLTK, but who didn't directly contribute it:

nltk/probability.py

@@ -1904,7 +1904,7 @@ def plot(self, *args, **kwargs):
         :type conditions: list
         """
         try:
-            from matplotlib import plt
+            import matplotlib.pyplot as plt #import statment fix
         except ImportError:
             raise ValueError(
                 'The plot function requires matplotlib to be installed.'
@@ -1913,40 +1913,46 @@ def plot(self, *args, **kwargs):
 
         cumulative = _get_kwarg(kwargs, 'cumulative', False)
         percents = _get_kwarg(kwargs, 'percents', False)
-        conditions = _get_kwarg(kwargs, 'conditions', sorted(self.conditions()))
+        conditions = [c for c in _get_kwarg(kwargs, 'conditions', self.conditions()) if c in self] # conditions should be in self
         title = _get_kwarg(kwargs, 'title', '')
         samples = _get_kwarg(
-            kwargs, 'samples', sorted(set(v for c in conditions
-                                          if v in self
-                                          for v in self[c]))
+            kwargs, 'samples', sorted(set(v 
+                                            for c in conditions
+                                            for v in self[c]))
         )  # this computation could be wasted
         if "linewidth" not in kwargs:
             kwargs["linewidth"] = 2
-
-        for condition in conditions:
-            if cumulative:
-                freqs = list(self[condition]._cumulative_frequencies(samples))
-                ylabel = "Cumulative Counts"
-                legend_loc = 'lower right'
-                if percents:
-                    freqs = [f / freqs[len(freqs) - 1] * 100 for f in freqs]
-                    ylabel = "Cumulative Percents"
-            else:
-                freqs = [self[condition][sample] for sample in samples]
-                ylabel = "Counts"
-                legend_loc = 'upper right'
-            # percents = [f * 100 for f in freqs] only in ConditionalProbDist?
-            kwargs['label'] = "%s" % condition
-            ax.plot(freqs, *args, **kwargs)
-
-
-        ax.legend(loc=legend_loc)
-        ax.grid(True, color="silver")
-        ax.set_xticks(range(len(samples)), [text_type(s) for s in samples], rotation=90)
-        if title:
-            ax.set_title(title)
-        ax.set_xlabel("Samples")
-        ax.set_ylabel(ylabel)
+        ax = plt.gca()
+        if (len(conditions) != 0):
+            freqs = []
+            for condition in conditions:
+                if cumulative:
+                    # freqs should be a list of list where each sub list will be a frequency of a condition
+                    freqs.append(list(self[condition]._cumulative_frequencies(samples)))
+                    ylabel = "Cumulative Counts"
+                    legend_loc = 'lower right'
+                    if percents:
+                        freqs[-1] = [f / freqs[len(freqs) - 1] * 100 for f in freqs]
+                        ylabel = "Cumulative Percents"
+                else:
+                    freqs.append([self[condition][sample] for sample in samples])
+                    ylabel = "Counts"
+                    legend_loc = 'upper right'
+                # percents = [f * 100 for f in freqs] only in ConditionalProbDist?
+
+            i = 0
+            for freq in freqs:
+                kwargs['label'] = conditions[i] #label for each condition
+                i += 1
+                ax.plot(freq, *args, **kwargs)
+            ax.legend(loc=legend_loc)
+            ax.grid(True, color="silver")
+            ax.set_xticks(range(len(samples)))
+            ax.set_xticklabels([text_type(s) for s in samples], rotation=90)
+            if title:
+                ax.set_title(title)
+            ax.set_xlabel("Samples")
+            ax.set_ylabel(ylabel)
         plt.show()
 
         return ax

nltk/test/unit/test_cfd_mutation.py

@@ -16,7 +16,7 @@ def test_plot(self):
         empty = ConditionalFreqDist()
         self.assertEqual(empty.conditions(),[])
         try:
-            empty.plot(conditions="BUG") # nonexistent keys shouldn't be added
+            empty.plot(conditions=["BUG"]) # nonexistent keys shouldn't be added
         except:
             pass
         self.assertEqual(empty.conditions(),[])