Skipping certain values in Python with Matplotlib

Question

I am currently working on an intra-day stock chart using the Alpha Vantage API. The data frame contains values from 4:00 to 20:00. In my matplotlib.pyplot chart however, the x-Axis also includes values from 20:00 to 4:00 over night. I dont want this as it messes up the aesthetics and also the Volume subplot.

Q: Is there any way to skip x-Axis values which dont exist in the actual Data Frame (the values from 20:00 to 04:00)?

As you can see, the Data Frame clearly jumps from 20:00 to 04:00

However in the Matplotlib chart, the x-Axis contains the values from 20:00 to 4:00, messing with the chart

Code so far. I believe so far everything is right:

import pandas as pd
import matplotlib.pyplot as plt
from alpha_vantage.timeseries import TimeSeries
import time
import datetime as dt
from datetime import timedelta as td 
from dateutil.relativedelta import relativedelta

#Accessing and Preparing API
ts = TimeSeries(key=api_key, output_format='pandas')

ticker_input = "TSLA"
interval_input = "15min"
df, meta_data = ts.get_intraday(symbol = ticker_input, interval = interval_input, outputsize = 'full')
slice_date = 16*4*5
df = df[0:slice_date]
df = df.iloc[::-1]
df["100ma"] = df["4. close"].rolling(window = 50, min_periods = 0).mean()
df["Close"] = df["4. close"]
df["Date"] = df.index

#Plotting all as 2 different subplots
ax1 = plt.subplot2grid((7,1), (0,0), rowspan = 5, colspan = 1)
ax1.plot(df["Date"], df['Close'])
ax1.plot(df["Date"], df["100ma"], linewidth = 0.5)
plt.xticks(rotation=45)
ax2 = plt.subplot2grid((6,1), (5,0), rowspan = 2, colspan = 2, sharex = ax1)
ax2.bar(df["Date"], df["5. volume"])
ax2.axes.xaxis.set_visible(False)
plt.tight_layout()
plt.show()

It would be great if anybody could help. Im still a complete beginner and only started Python 2 weeks ago.

Maybe this helps: https://stackoverflow.com/questions/51641983/exclude-range-of-dates-in-matplotlib — xDreamCoding, Aug 18 '20 at 20:50
The question is similar, but that one also doesn't have any answers. also the matplotlib site doesnt really help because that limits an exact y value. I want to skip it every time when it hits 20:00, whether it is 18-08-2020 20:00 or 25-12-2025 20:00. Therefore that solution doesnt really apply to mine — Leon_K, Aug 18 '20 at 20:58
Here: https://stackoverflow.com/questions/35085830/python-pandas-plot-time-series-with-gap — xDreamCoding, Aug 18 '20 at 21:11
Also maybe here: https://stackoverflow.com/questions/4152396/plotting-sparce-time-with-matplotlib — xDreamCoding, Aug 18 '20 at 21:14

score 1 · Answer 1 · answered Aug 19 '20 at 03:42

We got the data from the same place, although the data acquisition method is different. After extracting it in 15 units, I created a graph by excluding the data after 8pm and before 4pm. I created the code with the understanding that your skip would open up the pause. What you want it to skip is skipped once the NaN is set.

import datetime
import pandas as pd
import numpy as np
import pandas_datareader.data as web
import mplfinance as mpf
# import matplotlib.pyplot as plt

with open('./alpha_vantage_api_key.txt') as f:
    api_key = f.read()

now_ = datetime.datetime.today()

start = datetime.datetime(2019, 1, 1)
end = datetime.datetime(now_.year, now_.month, now_.day - 1)

symbol = 'TSLA'
df = web.DataReader(symbol, 'av-intraday', start, end, api_key=api_key)

df.columns = ['Open', 'High', 'Low', 'Close', 'Volume']
df.index = pd.to_datetime(df.index)
df["100ma"] = df["Close"].rolling(window = 50, min_periods = 0).mean()
df["Date"] = df.index
df_15 = df.asfreq('15min')
df_15 = df_15[(df_15.index.hour >= 4)&(df_15.index.hour <= 20) ]

import matplotlib.pyplot as plt
fig = plt.figure(figsize=(8,4.5),dpi=144)

#Plotting all as 2 different subplots
ax1 = plt.subplot2grid((7,1), (0,0), rowspan = 5, colspan = 1)
ax1.plot(df_15["Date"], df_15['Close'])
ax1.plot(df_15["Date"], df_15["100ma"], linewidth = 0.5)
plt.xticks(rotation=20)

ax2 = plt.subplot2grid((6,1), (5,0), rowspan = 2, colspan = 2, sharex = ax1)
ax2.bar(df_15["Date"], df_15["Volume"])
ax2.axes.xaxis.set_visible(False)
# plt.tight_layout()
plt.show()

score 0 · Accepted Answer · answered Aug 19 '20 at 14:54

I fixed it using matplotlib.ticker.formatter.

I first created a class and using:

class MyFormatter(Formatter):
    def __init__(self, dates, fmt='%Y-%m-%d %H:%M'):
        self.dates = dates
        self.fmt = fmt

    def __call__(self, x, pos=0):
        'Return the label for time x at position pos'
        ind = int(np.round(x))
    if ind >= len(self.dates) or ind < 0:
        return ''
    return self.dates[ind].strftime(self.fmt)

formatter = MyFormatter(df.index)
ax1 = plt.subplot2grid((7,1), (0,0), rowspan = 5, colspan = 1)
ax1.xaxis.set_major_formatter(formatter)
ax1.plot(np.arange(len(df)), df["Close"])
ax1.plot(np.arange(len(df)), df["100ma"], linewidth = 0.5)
ax1.xticks(rotation=45)
ax1.axis([xmin,xmax,ymin,ymax])
ax2 = plt.subplot2grid((6,1), (5,0), rowspan = 2, colspan = 2, sharex = ax1)
ax2.bar(np.arange(len(df)), df["5. volume"])

plt.show()

This gave me a smoother graph than the one before and also that recommended by r-beginner.

The only issue that I have is that if I zoom in the x-axis doesnt really change. it always has teh year, month, date, hour, and minute. Obviously I only want hour and minute when Im zoomed in further. I am yet to figure out how to do that

Skipping certain values in Python with Matplotlib

2 Answers2