Convert string to matplotlib date for plotting - python-3.x

Question

I've been trying to convert string date into a format that can be plotted on a graph.
The code
import matplotlib.pyplot as plt
import numpy as np
import urllib
import matplotlib.dates as mdates
import datetime
def graph_data():
fig=plt.figure()
ax1=plt.subplot2grid((1,1),(0,0))
stock_price_url = 'https://pythonprogramming.net/yahoo_finance_replacement'
source_code = urllib.request.urlopen(stock_price_url).read().decode()
stock_data = []
split_source=source_code.split('\n')
print(len(split_source))
for line in split_source[1:]:
stock_data.append(line)
date,openn,closep,highp,lowp,openp,volume=np.loadtxt(stock_data,delimiter=',',unpack=True)
x = [datetime.strptime(d, '%Y-%m-%d') for d in date]
ax1.plot_date(x,closep,'-',linewidth=0.1)
plt.xlabel('x')
plt.ylabel('y')
plt.title('Graph')
plt.show()
graph_data()
Any method of conversion just gives the same error
ValueError: could not convert string to float: '2017-07-26'
What method can I use to convert the string into date that can be plotted

Answer 1

Ther's nothing wrong with your code. The problem is with the data.
If you look at the data, you will find that from date to volume features your data is a string like this :
data = '2017-07-26,153.3500,153.9300,153.0600,153.5000,153.5000,12778195.00'.
That is the representation of a string.
So you need to do some preprocessing first. There may be various methods to do so.
I found this method helpful to me:
First, you have to remove the commas in data and replace them with spaces and then use the split function to convert data into a split format.
So, you need to make these changes in your code:
date = []
closep = []
for i in range(len(stock_data)):
temp = stock_data[i].replace(',', ' ').split()
date.append(temp[0])
closep.append(temp[2])
0 and two are the positions of date and closep in your dataset.
Now instead of 'x' and 'closep' as you have used in your plot method, use these 'date ' and 'closep' I just shared you via code.
One more thing is that the graph is having trouble with this big dataset I think.
So use date[0:100], closep[0:100] to try the plot for smaller dataset.
The complete code would look like this:
import matplotlib.pyplot as plt
import numpy as np
import urllib
import matplotlib.dates as mdates
import datetime
def graph_data():
fig = plt.figure()
ax1 = plt.subplot2grid((1, 1), (0, 0))
stock_price_url =
'https://pythonprogramming.net/yahoo_finance_replacement'
source_code = urllib.request.urlopen(stock_price_url).read().decode()
stock_data = []
split_source = source_code.split('\n')
for line in split_source[1:]:
stock_data.append(line)
date = []
closep = []
for i in range(len(stock_data)):
temp = stock_data[i].replace(',', ' ').split()
date.append(temp[0])
closep.append(temp[2])
ax1.plot_date(date[0:100], closep[0:100], '-', linewidth=0.1)
plt.xlabel('x')
plt.ylabel('y')
plt.title('Graph')
plt.show()
graph_data()
Hope this helps.