diff --git a/script/utils.py b/script/utils.py
index 154fe95..80a59e5 100644
--- a/script/utils.py
+++ b/script/utils.py
@@ -332,3 +332,34 @@ def construct_sentences(p2_root, removed):
         if not removed_branches: 
             sentences.append(branch_str)
     return sentences
+
+
+def calculate_purity(true_col, pred_col, df): 
+    '''
+    Calculate harmonic purity between two set of clusterings
+    df: a Pandas data frame containing two columns (true_col and pred_col)
+    true_col: column containing a ground-truth label for each document 
+    pred_col: column containing a predicted label for each document
+    '''
+    contingency_matrix = metrics.cluster.contingency_matrix(df[true_col], df[pred_col]) 
+    precision = contingency_matrix / contingency_matrix.sum(axis=0).reshape(1, -1)
+    recall = contingency_matrix / contingency_matrix.sum(axis=1).reshape(-1, 1)
+    f1 = 2 * (precision * recall) / (precision + recall)
+    f1 = np.nan_to_num(f1)
+    purity = (np.amax(precision, axis=0) * contingency_matrix.sum(axis=0)).sum() / contingency_matrix.sum()
+    inverse_purity = (np.amax(recall, axis=1) * contingency_matrix.sum(axis=1)).sum() / contingency_matrix.sum()
+    harmonic_purity = (np.amax(f1, axis=1) * contingency_matrix.sum(axis=1)).sum() / contingency_matrix.sum()
+    return (purity, inverse_purity, harmonic_purity)
+
+
+def calculate_metrics(true_col, pred_col, df): 
+    '''
+    Calculate topic alignment between df1 and df2 (harmonic purity, ARI, NMI)
+    df: a Pandas data frame containing two columns (true_col and pred_col)
+    true_col: column containing a ground-truth label for each document 
+    pred_col: column containing a predicted label for each document
+    '''
+    purity, inverse_purity, harmonic_purity = calculate_purity(true_col, pred_col, df)
+    ari = metrics.adjusted_rand_score(df[true_col], df[pred_col])
+    mis = metrics.normalized_mutual_info_score(df[true_col], df[pred_col])
+    return (harmonic_purity, ari, mis)