blog updated

docs/blog/README.md

@@ -1,5 +1,81 @@
 # 博客
 
+## 2020.01.26 BOX 历史价格自动更新
+
+我在 github 仓库里，添加了一个 ```data``` 目录，里面的 BOX 历史价格文件会每日 23:59 更新一次价格。
+
+而后，可以使用这个文件去用 Python 制作价格变动图表，代码如下：
+
+
+
+```python
+import matplotlib.pyplot as plt
+import pandas as pd
+from re import sub
+
+series = pd.read_csv(
+    "https://raw.githubusercontent.com/xiaolai/regular-investing-in-box/master/data/box_price_history.txt",
+    sep="\t"
+)
+
+number_of_rows = series.shape[0]
+
+daily_invested = 1
+
+# add column "Total Invested"
+total_invested = []
+for i in range(0, number_of_rows):
+    total_invested.append((i+1)*daily_invested)
+series["Total Invested"] = total_invested
+
+# add column "Daily Bought"
+BOX_daily_bought = []
+for i in range(0, number_of_rows):
+    BOX_daily_bought.append(daily_invested/float(sub(r"[^\d.]", "", series.at[i, "BOX Price"])))
+
+series["BOX Bought"] = BOX_daily_bought
+
+# add column "Value Accumulated"
+value_accumulated = []
+for i in range(0, number_of_rows):
+    holding = 0
+    for j in range(0, i+1):
+        holding += series.at[j, "BOX Bought"]
+    value_accumulated.append(holding * float(sub(r"[^\d.]", "", series.at[i, "BOX Price"])))
+series["Value Accumulated"] = value_accumulated    
+
+
+# add BTC price change
+btc_price_change = []
+eos_price_change = []
+xin_price_change = []
+box_price_change = []
+ri_box_change = []
+for i in range(0, number_of_rows):
+    btc_price_change.append(float(sub(r"[^\d.]", "", series.at[i, "BTC Price"]))/float(sub(r"[^\d.]", "", series.at[0, "BTC Price"])) - 1)
+    eos_price_change.append(float(sub(r"[^\d.]", "", series.at[i, "EOS Price"]))/float(sub(r"[^\d.]", "", series.at[0, "EOS Price"])) - 1)
+    xin_price_change.append(float(sub(r"[^\d.]", "", series.at[i, "XIN Price"]))/float(sub(r"[^\d.]", "", series.at[0, "XIN Price"])) - 1)
+    box_price_change.append(float(sub(r"[^\d.]", "", series.at[i, "BOX Price"]))/float(sub(r"[^\d.]", "", series.at[0, "BOX Price"])) - 1)    
+    ri_box_change.append(series.at[i, "Value Accumulated"]/series.at[i, "Total Invested"] - 1)
+series["BTC"] = btc_price_change
+series["EOS"] = eos_price_change
+series["XIN"] = xin_price_change
+series["BOX"] = box_price_change
+series["RI-BOX"] = ri_box_change
+
+# print(series)
+
+ax = plt.gca()
+series.plot(kind='line', x='Date', y='BTC', ax=ax)
+series.plot(kind='line', x='Date', y='EOS', ax=ax)
+series.plot(kind='line', x='Date', y='XIN', ax=ax)
+series.plot(kind='line', x='Date', y='BOX', ax=ax)
+series.plot(kind='line', x='Date', y='RI-BOX', ax=ax)
+plt.show()
+```
+
+![png](images/output_0_0.png)
+
 ## 2020.01.24 多年前的一篇短文
 
 我曾经用过 xiaolai.li 这个域名，后来不用了。现在，这篇文章只能在 [archive.org](https://web.archive.org/web/20140523062542/xiaolai.li/bitcoin-period) 上看到了。