Add plot script

.gitignore

@@ -1,6 +1,12 @@
 .env
 .vscode
+# python virtual environment
+venv
 
 # go executable
 hnbot
 hnbot.sqlite3
+
+*.csv
+*.png
+

plot.py

@@ -0,0 +1,60 @@
+#!/usr/bin/env python3
+
+import pandas as pd
+import matplotlib.pyplot as plt
+import matplotlib.dates as mdates
+from datetime import timedelta, datetime
+
+# this script loads data from a csv file
+# with headers id, created_at, time, title, url, author, ndescendants, score, rank
+# and then saves a plot with score, ndescendants and rank for each id
+
+# load data from csv file
+df = pd.read_csv('hacker_news.csv', index_col='created_at')
+
+# group pandas dataframe by id
+grouped = df.groupby(['id'])
+
+# create one chart per id and plot score, ndescendants and rank in each chart
+for [hn_id], group in grouped:
+    # sort group by created_at ascending
+    group = group.sort_values(by='created_at', ascending=True)
+
+    # this is the time when the item was created on HN
+    item_created_at = datetime.utcfromtimestamp(group['time'].values[0])
+
+    # use relative time for x axis
+    def date_to_relative(d1):
+        date_fmt = '%Y-%m-%d %H:%M:%S'
+        current = datetime.strptime(d1, date_fmt)
+        return (current - item_created_at) / timedelta(hours=1)
+
+    group.index = group.index.map(date_to_relative)
+
+    # title generation
+    hn_item_title = group['title'].values[0]
+    hn_item_url = group['url'].values[0]
+    hn_item_link = f'https://news.ycombinator.com/item?id={hn_id}'
+    plot_title = f'{hn_item_title}\n{hn_item_url}\n{hn_item_link}'
+
+    fig, ax1 = plt.subplots(figsize=(10, 5))
+
+    ax1.set_title(plot_title)
+    ax1.set_xlabel('hours')
+    ax1.set_ylabel('score, comments')
+    ax1.plot(group['score'], label='score', color='blue')
+    ax1.plot(group['ndescendants'], label='comments', color='orange')
+    ax1.legend()
+
+    # show every 50th date
+    # TODO: do something more clever here
+    plt.xticks(group.index[::50], rotation=45)
+
+    ax2 = ax1.twinx()
+    ax2.set_ylabel('rank')
+    ax2.set_ylim(1, 30)
+    ax2.plot(group['rank'], label='rank', color='green')
+    ax2.legend(loc='upper right')
+
+    plt.tight_layout()
+    plt.savefig(f'hn_{hn_id}.png')