Gets list of terms to display that have some interesting diachronic variation.

		Returns
		-------
		pd.DataFrame

		e.g.,
		           term variable  frequency  trending
		2            in   200310        1.0  0.000000
		19          for   200310        1.0  0.000000
		20           to   200311        1.0  0.000000

def get_display_dataframe(self):
		'''
		Gets list of terms to display that have some interesting diachronic variation.

		Returns
		-------
		pd.DataFrame

		e.g.,
		           term variable  frequency  trending
		2            in   200310        1.0  0.000000
		19          for   200310        1.0  0.000000
		20           to   200311        1.0  0.000000
		'''
		X = self.corpus_.get_term_doc_mat()
		categories = pd.Series(self.corpus_.get_category_ids())
		cat_ar = np.array(self.corpus_.get_categories())
		cat_idx_sort = np.argsort(cat_ar)
		if self.seasonality_column_:
			print('YES')
			seasonality_ar = np.array(self.corpus_.get_df()[self.seasonality_column_])

		terms = self.corpus_.get_terms()
		category_idx_store = self.corpus_.get_category_index_store()

		data = {}
		seasondata = {}
		for i, cati in enumerate(cat_idx_sort):
			cat = cat_ar[cati]
			if cat >= self.start_category_ and i > self.timesteps_to_lag_:
				neg_cats = self.sorted_categores_[i - self.timesteps_to_lag_:i]
				neg_mask = categories.isin(category_idx_store.getidxstrictbatch(neg_cats)).values
				scores = self._regress_terms(X, cat, categories, category_idx_store, neg_mask, terms)
				data[cat] = scores
				if self.seasonality_column_:
					neg_cats = set(categories[(seasonality_ar == seasonality_ar[cati]) & (categories != categories[cati])])
					neg_mask = categories.isin(neg_cats).values
					scores = self._regress_terms(X, cat, categories, category_idx_store, neg_mask, terms)
					seasondata[cat] = scores
		coefs = pd.DataFrame(data)
		pos_coefs = (coefs.apply(lambda x: (x > 0) * x, axis=1)
		             .sum(axis=1)
		             .sort_values(ascending=False))

		term_cat_counts = self.corpus_.get_term_freq_df('')[coefs.columns]

		def dense_percentile(x):
			# ranks = rankdata(x, 'dense')
			return pd.Series(x / x.max(), index=x.index)

		rank_df = pd.DataFrame({'coefr': dense_percentile(pos_coefs),
		                        'freqr': dense_percentile(term_cat_counts.max(axis=1)),
		                        'coef': pos_coefs,
		                        'freq': term_cat_counts.max(axis=1)})
		if self.seasonality_column_:
			seasoncoefs = (pd.DataFrame(seasondata).sum(axis=1))
			rank_df['seasoncoefr'] = dense_percentile(seasoncoefs.sort_values(ascending=False) + np.abs(seasoncoefs.min()))
			weights = [2, 1, 1]
			vals = ['freqr', 'coefr', 'seasoncoefr']

			def gethmean(x):
				if min(x[vals]) == 0:
					return 0
				return sum(weights) * 1. / sum([weights[i] / x[val] for i, val in enumerate(vals)])

			rank_df['hmean'] = rank_df.apply(gethmean, axis=1)
		else:
			beta = 0.5
			rank_df['hmean'] = (rank_df
			                    .apply(lambda x: 0 if min(x) == 0 else
			(1 + beta ** 2) * (x.coefr * x.freqr) / ((beta ** 2 * x.coefr) + x.freqr),
			                           axis=1))
		rank_df = rank_df.sort_values(by='hmean', ascending=False)
		display_df = pd.merge((term_cat_counts
		                       .loc[rank_df.iloc[:self.num_terms_].index]
		                       .reset_index()
		                       .melt(id_vars=['index'])
		                       .rename(columns={'index': 'term', 'value': 'frequency'})),
		                      (coefs.loc[rank_df.iloc[:self.num_terms_].index]
		                       .reset_index()
		                       .melt(id_vars=['index'])
		                       .rename(columns={'index': 'term', 'value': 'trending'})),
		                      on=['term', 'variable'])
		display_df[display_df['frequency'] == 0] = np.nan
		display_df = display_df.dropna()
		return display_df[display_df.term.isin(rank_df.index)]