%matplotlib inline
import time
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
from datetime import datetime
#df = pd.read_json('daily.json') # df[0].dtype: dtype('int64'), df[1].dtype: dtype('float64')
df = pd.read_json('daily.json', dtype={ 0: 'int64', 1: 'float64', 2: 'float64', 3: 'float64', 4: 'float64' })
#df['DATE'] = pd.Series([datetime.fromtimestamp(time.mktime(time.localtime(x / 1000))) for x in df[0]])
#df['USDJPY'] = pd.Series([float(x) for x in df[4]])
df['DATE'] = pd.to_datetime(df[0], unit='ms')
df['USDJPY'] = df[4].astype('float64')
df.plot(x='DATE', y='USDJPY')
<matplotlib.axes._subplots.AxesSubplot at 0x7f05eda67828>