Advanced Matplotlib Series (videos and ending source only)

Once you have a basic understanding of how Matplotlib works, you might have an interest in taking your knowledge a bit further. Some of the most complex graphing needs come in the form of stock analysis and charting, or Forex. In this tutorial series, we're going to cover where and how to automatically grab, sort, and organize some free stock and forex pricing data. Next, we're going to chart it using some of the more popular indicators as an example. Here, we'll do MACD (Moving Average Convergence Divergence) and the RSI (Relative Strength Index). To help us calculate these, we will use NumPy, but otherwise we will calculate these all on our own.

To acquire the data, we're going to use the Yahoo finance API. This API returns historical price data for the ticker symbol we specify and for the time length we ask for. The larger the time frame, the lower the resolution of data we get. So, if you ask for a 1-day time frame for AAPL, you will get 3-minute OHLC (open high low close) data. If you ask for 10 years worth, you will get daily data, or even 3 day time frames. Keep this in mind and choose a time frame that fits your goals. Also, if you choose a low enough time frame and get high enough granularity, the API will return the time in a unix time stamp, as compared to a date stamp.

Once we have the data, we will want to graph it. To start, we'll just plot the lines, but most people will want to plot a candlestick instead. We will use Matplotlib's candlestick function, and make a simple edit to it to improve it slightly. On this same chart, we'll also overlay a few moving average calculations.

After this, we're going to create a subplot, and graph the volume. We cannot plot volume on the same subplot immediately, because the scale is different. To start, we will plot the volume underneath in another sub plot, but eventually we'll actually overlay volume on the same figure and make it somewhat transparent.

Then, we're going to add 2 sub plots and plot an RSI indicator on top and the MACD indicator on the bottom. For all of these, we're going to share the X axis, so we can zoom in and out in 1 plot and they will all match the same time frame.

We're going to plot in date format for the X axis, and customize just about all of the things we can for aesthetics. This includes changing tick label colors, edge / spine colors, line colors, OHLC candlestick colors, learn how to create a filled graph (for volume), histograms, draw specific lines (hline for RSI), and a whole lot more.

Here's the end-result (I have both a Python 3 and a Python 2 version for this. Python 3 first, then Python 2. Make sure you're using the one that matches your Python Version!):

# THIS VERSION IS FOR PYTHON 3 #
import urllib.request, urllib.error, urllib.parse
import time
import datetime
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.ticker as mticker
import matplotlib.dates as mdates
from matplotlib.finance import candlestick_ohlc
import matplotlib
import pylab
matplotlib.rcParams.update({'font.size': 9})

def rsiFunc(prices, n=14):
    deltas = np.diff(prices)
    seed = deltas[:n+1]
    up = seed[seed>=0].sum()/n
    down = -seed[seed<0].sum()/n
    rs = up/down
    rsi = np.zeros_like(prices)
    rsi[:n] = 100. - 100./(1.+rs)

    for i in range(n, len(prices)):
        delta = deltas[i-1] # cause the diff is 1 shorter

        if delta>0:
            upval = delta
            downval = 0.
        else:
            upval = 0.
            downval = -delta

        up = (up*(n-1) + upval)/n
        down = (down*(n-1) + downval)/n

        rs = up/down
        rsi[i] = 100. - 100./(1.+rs)

    return rsi

def movingaverage(values,window):
    weigths = np.repeat(1.0, window)/window
    smas = np.convolve(values, weigths, 'valid')
    return smas # as a numpy array


def ExpMovingAverage(values, window):
    weights = np.exp(np.linspace(-1., 0., window))
    weights /= weights.sum()
    a =  np.convolve(values, weights, mode='full')[:len(values)]
    a[:window] = a[window]
    return a


def computeMACD(x, slow=26, fast=12):
    """
    compute the MACD (Moving Average Convergence/Divergence) using a fast and slow exponential moving avg'
    return value is emaslow, emafast, macd which are len(x) arrays
    """
    emaslow = ExpMovingAverage(x, slow)
    emafast = ExpMovingAverage(x, fast)
    return emaslow, emafast, emafast - emaslow


def bytespdate2num(fmt, encoding='utf-8'):
    strconverter = mdates.strpdate2num(fmt)
    def bytesconverter(b):
        s = b.decode(encoding)
        return strconverter(s)
    return bytesconverter

def graphData(stock,MA1,MA2):

    '''
        Use this to dynamically pull a stock:
    '''
    try:
        print('Currently Pulling',stock)
        urlToVisit = 'http://chartapi.finance.yahoo.com/instrument/1.0/'+stock+'/chartdata;type=quote;range=10y/csv'
        stockFile =[]
        try:
            sourceCode = urllib.request.urlopen(urlToVisit).read().decode()
            splitSource = sourceCode.split('\n')
            for eachLine in splitSource:
                splitLine = eachLine.split(',')
                if len(splitLine)==6:
                    if 'values' not in eachLine:
                        stockFile.append(eachLine)
        except Exception as e:
            print(str(e), 'failed to organize pulled data.')
    except Exception as e:
        print(str(e), 'failed to pull pricing data')

    try:
        date, closep, highp, lowp, openp, volume = np.loadtxt(stockFile,delimiter=',', unpack=True,
                                                              converters={ 0: bytespdate2num('%Y%m%d')})
        x = 0
        y = len(date)
        newAr = []
        while x < y:
            appendLine = date[x],openp[x],highp[x],lowp[x],closep[x],volume[x]
            newAr.append(appendLine)
            x+=1
            
        Av1 = movingaverage(closep, MA1)
        Av2 = movingaverage(closep, MA2)

        SP = len(date[MA2-1:])
            
        fig = plt.figure(facecolor='#07000d')

        ax1 = plt.subplot2grid((6,4), (1,0), rowspan=4, colspan=4, axisbg='#07000d')
        candlestick_ohlc(ax1, newAr[-SP:], width=.6, colorup='#53c156', colordown='#ff1717')

        Label1 = str(MA1)+' SMA'
        Label2 = str(MA2)+' SMA'

        ax1.plot(date[-SP:],Av1[-SP:],'#e1edf9',label=Label1, linewidth=1.5)
        ax1.plot(date[-SP:],Av2[-SP:],'#4ee6fd',label=Label2, linewidth=1.5)
        
        ax1.grid(True, color='w')
        ax1.xaxis.set_major_locator(mticker.MaxNLocator(10))
        ax1.xaxis.set_major_formatter(mdates.DateFormatter('%Y-%m-%d'))
        ax1.yaxis.label.set_color("w")
        ax1.spines['bottom'].set_color("#5998ff")
        ax1.spines['top'].set_color("#5998ff")
        ax1.spines['left'].set_color("#5998ff")
        ax1.spines['right'].set_color("#5998ff")
        ax1.tick_params(axis='y', colors='w')
        plt.gca().yaxis.set_major_locator(mticker.MaxNLocator(prune='upper'))
        ax1.tick_params(axis='x', colors='w')
        plt.ylabel('Stock price and Volume')

        maLeg = plt.legend(loc=9, ncol=2, prop={'size':7},
                   fancybox=True, borderaxespad=0.)
        maLeg.get_frame().set_alpha(0.4)
        textEd = pylab.gca().get_legend().get_texts()
        pylab.setp(textEd[0:5], color = 'w')

        volumeMin = 0
        
        ax0 = plt.subplot2grid((6,4), (0,0), sharex=ax1, rowspan=1, colspan=4, axisbg='#07000d')
        rsi = rsiFunc(closep)
        rsiCol = '#c1f9f7'
        posCol = '#386d13'
        negCol = '#8f2020'
        
        ax0.plot(date[-SP:], rsi[-SP:], rsiCol, linewidth=1.5)
        ax0.axhline(70, color=negCol)
        ax0.axhline(30, color=posCol)
        ax0.fill_between(date[-SP:], rsi[-SP:], 70, where=(rsi[-SP:]>=70), facecolor=negCol, edgecolor=negCol, alpha=0.5)
        ax0.fill_between(date[-SP:], rsi[-SP:], 30, where=(rsi[-SP:]<=30), facecolor=posCol, edgecolor=posCol, alpha=0.5)
        ax0.set_yticks([30,70])
        ax0.yaxis.label.set_color("w")
        ax0.spines['bottom'].set_color("#5998ff")
        ax0.spines['top'].set_color("#5998ff")
        ax0.spines['left'].set_color("#5998ff")
        ax0.spines['right'].set_color("#5998ff")
        ax0.tick_params(axis='y', colors='w')
        ax0.tick_params(axis='x', colors='w')
        plt.ylabel('RSI')

        ax1v = ax1.twinx()
        ax1v.fill_between(date[-SP:],volumeMin, volume[-SP:], facecolor='#00ffe8', alpha=.4)
        ax1v.axes.yaxis.set_ticklabels([])
        ax1v.grid(False)
        ###Edit this to 3, so it's a bit larger
        ax1v.set_ylim(0, 3*volume.max())
        ax1v.spines['bottom'].set_color("#5998ff")
        ax1v.spines['top'].set_color("#5998ff")
        ax1v.spines['left'].set_color("#5998ff")
        ax1v.spines['right'].set_color("#5998ff")
        ax1v.tick_params(axis='x', colors='w')
        ax1v.tick_params(axis='y', colors='w')
        ax2 = plt.subplot2grid((6,4), (5,0), sharex=ax1, rowspan=1, colspan=4, axisbg='#07000d')
        fillcolor = '#00ffe8'
        nslow = 26
        nfast = 12
        nema = 9
        emaslow, emafast, macd = computeMACD(closep)
        ema9 = ExpMovingAverage(macd, nema)
        ax2.plot(date[-SP:], macd[-SP:], color='#4ee6fd', lw=2)
        ax2.plot(date[-SP:], ema9[-SP:], color='#e1edf9', lw=1)
        ax2.fill_between(date[-SP:], macd[-SP:]-ema9[-SP:], 0, alpha=0.5, facecolor=fillcolor, edgecolor=fillcolor)

        plt.gca().yaxis.set_major_locator(mticker.MaxNLocator(prune='upper'))
        ax2.spines['bottom'].set_color("#5998ff")
        ax2.spines['top'].set_color("#5998ff")
        ax2.spines['left'].set_color("#5998ff")
        ax2.spines['right'].set_color("#5998ff")
        ax2.tick_params(axis='x', colors='w')
        ax2.tick_params(axis='y', colors='w')
        plt.ylabel('MACD', color='w')
        ax2.yaxis.set_major_locator(mticker.MaxNLocator(nbins=5, prune='upper'))
        for label in ax2.xaxis.get_ticklabels():
            label.set_rotation(45)

        plt.suptitle(stock.upper(),color='w')
        plt.setp(ax0.get_xticklabels(), visible=False)
        plt.setp(ax1.get_xticklabels(), visible=False)
        
        ax1.annotate('Big news!',(date[510],Av1[510]),
            xytext=(0.8, 0.9), textcoords='axes fraction',
            arrowprops=dict(facecolor='white', shrink=0.05),
            fontsize=14, color = 'w',
            horizontalalignment='right', verticalalignment='bottom')

        plt.subplots_adjust(left=.09, bottom=.14, right=.94, top=.95, wspace=.20, hspace=0)
        plt.show()
        fig.savefig('example.png',facecolor=fig.get_facecolor())
           
    except Exception as e:
        print('main loop',str(e))

while True:
    stock = input('Stock to plot: ')
    graphData(stock,10,50)

# THIS VERSION IS FOR PYTHON 2 #
import urllib2
import time
import datetime
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.ticker as mticker
import matplotlib.dates as mdates
from matplotlib.finance import candlestick
import matplotlib
import pylab
matplotlib.rcParams.update({'font.size': 9})

eachStock = 'EBAY','TSLA','AAPL'

def rsiFunc(prices, n=14):
    deltas = np.diff(prices)
    seed = deltas[:n+1]
    up = seed[seed>=0].sum()/n
    down = -seed[seed<0].sum()/n
    rs = up/down
    rsi = np.zeros_like(prices)
    rsi[:n] = 100. - 100./(1.+rs)

    for i in range(n, len(prices)):
        delta = deltas[i-1] # cause the diff is 1 shorter

        if delta>0:
            upval = delta
            downval = 0.
        else:
            upval = 0.
            downval = -delta

        up = (up*(n-1) + upval)/n
        down = (down*(n-1) + downval)/n

        rs = up/down
        rsi[i] = 100. - 100./(1.+rs)

    return rsi

def movingaverage(values,window):
    weigths = np.repeat(1.0, window)/window
    smas = np.convolve(values, weigths, 'valid')
    return smas # as a numpy array

def ExpMovingAverage(values, window):
    weights = np.exp(np.linspace(-1., 0., window))
    weights /= weights.sum()
    a =  np.convolve(values, weights, mode='full')[:len(values)]
    a[:window] = a[window]
    return a


def computeMACD(x, slow=26, fast=12):
    """
    compute the MACD (Moving Average Convergence/Divergence) using a fast and slow exponential moving avg'
    return value is emaslow, emafast, macd which are len(x) arrays
    """
    emaslow = ExpMovingAverage(x, slow)
    emafast = ExpMovingAverage(x, fast)
    return emaslow, emafast, emafast - emaslow

def graphData(stock,MA1,MA2):
    '''
        Use this to dynamically pull a stock:
    '''
    try:
        print 'Currently Pulling',stock
        print str(datetime.datetime.fromtimestamp(int(time.time())).strftime('%Y-%m-%d %H:%M:%S'))
        urlToVisit = 'http://chartapi.finance.yahoo.com/instrument/1.0/'+stock+'/chartdata;type=quote;range=10y/csv'
        stockFile =[]
        try:
            sourceCode = urllib2.urlopen(urlToVisit).read()
            splitSource = sourceCode.split('\n')
            for eachLine in splitSource:
                splitLine = eachLine.split(',')
                if len(splitLine)==6:
                    if 'values' not in eachLine:
                        stockFile.append(eachLine)
        except Exception, e:
            print str(e), 'failed to organize pulled data.'
    except Exception,e:
        print str(e), 'failed to pull pricing data'
    try:   
        date, closep, highp, lowp, openp, volume = np.loadtxt(stockFile,delimiter=',', unpack=True,
                                                              converters={ 0: mdates.strpdate2num('%Y%m%d')})
        x = 0
        y = len(date)
        newAr = []
        while x < y:
            appendLine = date[x],openp[x],closep[x],highp[x],lowp[x],volume[x]
            newAr.append(appendLine)
            x+=1
            
        Av1 = movingaverage(closep, MA1)
        Av2 = movingaverage(closep, MA2)

        SP = len(date[MA2-1:])
            
        fig = plt.figure(facecolor='#07000d')

        ax1 = plt.subplot2grid((6,4), (1,0), rowspan=4, colspan=4, axisbg='#07000d')
        candlestick(ax1, newAr[-SP:], width=.6, colorup='#53c156', colordown='#ff1717')

        Label1 = str(MA1)+' SMA'
        Label2 = str(MA2)+' SMA'

        ax1.plot(date[-SP:],Av1[-SP:],'#e1edf9',label=Label1, linewidth=1.5)
        ax1.plot(date[-SP:],Av2[-SP:],'#4ee6fd',label=Label2, linewidth=1.5)
        
        ax1.grid(True, color='w')
        ax1.xaxis.set_major_locator(mticker.MaxNLocator(10))
        ax1.xaxis.set_major_formatter(mdates.DateFormatter('%Y-%m-%d'))
        ax1.yaxis.label.set_color("w")
        ax1.spines['bottom'].set_color("#5998ff")
        ax1.spines['top'].set_color("#5998ff")
        ax1.spines['left'].set_color("#5998ff")
        ax1.spines['right'].set_color("#5998ff")
        ax1.tick_params(axis='y', colors='w')
        plt.gca().yaxis.set_major_locator(mticker.MaxNLocator(prune='upper'))
        ax1.tick_params(axis='x', colors='w')
        plt.ylabel('Stock price and Volume')

        maLeg = plt.legend(loc=9, ncol=2, prop={'size':7},
                   fancybox=True, borderaxespad=0.)
        maLeg.get_frame().set_alpha(0.4)
        textEd = pylab.gca().get_legend().get_texts()
        pylab.setp(textEd[0:5], color = 'w')

        volumeMin = 0
        
        ax0 = plt.subplot2grid((6,4), (0,0), sharex=ax1, rowspan=1, colspan=4, axisbg='#07000d')
        rsi = rsiFunc(closep)
        rsiCol = '#c1f9f7'
        posCol = '#386d13'
        negCol = '#8f2020'
        
        ax0.plot(date[-SP:], rsi[-SP:], rsiCol, linewidth=1.5)
        ax0.axhline(70, color=negCol)
        ax0.axhline(30, color=posCol)
        ax0.fill_between(date[-SP:], rsi[-SP:], 70, where=(rsi[-SP:]>=70), facecolor=negCol, edgecolor=negCol, alpha=0.5)
        ax0.fill_between(date[-SP:], rsi[-SP:], 30, where=(rsi[-SP:]<=30), facecolor=posCol, edgecolor=posCol, alpha=0.5)
        ax0.set_yticks([30,70])
        ax0.yaxis.label.set_color("w")
        ax0.spines['bottom'].set_color("#5998ff")
        ax0.spines['top'].set_color("#5998ff")
        ax0.spines['left'].set_color("#5998ff")
        ax0.spines['right'].set_color("#5998ff")
        ax0.tick_params(axis='y', colors='w')
        ax0.tick_params(axis='x', colors='w')
        plt.ylabel('RSI')

        ax1v = ax1.twinx()
        ax1v.fill_between(date[-SP:],volumeMin, volume[-SP:], facecolor='#00ffe8', alpha=.4)
        ax1v.axes.yaxis.set_ticklabels([])
        ax1v.grid(False)
        ###Edit this to 3, so it's a bit larger
        ax1v.set_ylim(0, 3*volume.max())
        ax1v.spines['bottom'].set_color("#5998ff")
        ax1v.spines['top'].set_color("#5998ff")
        ax1v.spines['left'].set_color("#5998ff")
        ax1v.spines['right'].set_color("#5998ff")
        ax1v.tick_params(axis='x', colors='w')
        ax1v.tick_params(axis='y', colors='w')
        ax2 = plt.subplot2grid((6,4), (5,0), sharex=ax1, rowspan=1, colspan=4, axisbg='#07000d')
        fillcolor = '#00ffe8'
        nslow = 26
        nfast = 12
        nema = 9
        emaslow, emafast, macd = computeMACD(closep)
        ema9 = ExpMovingAverage(macd, nema)
        ax2.plot(date[-SP:], macd[-SP:], color='#4ee6fd', lw=2)
        ax2.plot(date[-SP:], ema9[-SP:], color='#e1edf9', lw=1)
        ax2.fill_between(date[-SP:], macd[-SP:]-ema9[-SP:], 0, alpha=0.5, facecolor=fillcolor, edgecolor=fillcolor)

        plt.gca().yaxis.set_major_locator(mticker.MaxNLocator(prune='upper'))
        ax2.spines['bottom'].set_color("#5998ff")
        ax2.spines['top'].set_color("#5998ff")
        ax2.spines['left'].set_color("#5998ff")
        ax2.spines['right'].set_color("#5998ff")
        ax2.tick_params(axis='x', colors='w')
        ax2.tick_params(axis='y', colors='w')
        plt.ylabel('MACD', color='w')
        ax2.yaxis.set_major_locator(mticker.MaxNLocator(nbins=5, prune='upper'))
        for label in ax2.xaxis.get_ticklabels():
            label.set_rotation(45)

        plt.suptitle(stock.upper(),color='w')

        plt.setp(ax0.get_xticklabels(), visible=False)
        plt.setp(ax1.get_xticklabels(), visible=False)
        
        ax1.annotate('Big news!',(date[510],Av1[510]),
            xytext=(0.8, 0.9), textcoords='axes fraction',
            arrowprops=dict(facecolor='white', shrink=0.05),
            fontsize=14, color = 'w',
            horizontalalignment='right', verticalalignment='bottom')

        plt.subplots_adjust(left=.09, bottom=.14, right=.94, top=.95, wspace=.20, hspace=0)
        plt.show()
        fig.savefig('example.png',facecolor=fig.get_facecolor())
           
    except Exception,e:
        print 'main loop',str(e)

while True:
    stock = raw_input('Stock to plot: ')
    graphData(stock,10,50)

That's all for now. Want more tutorials? Head to the Home Page