Convert CSV to PNG with matplotlib Issue

Question

I am trying to create a PNG image with some CSV data but I am getting an error related to the date column (meanwhile converted to list). The error is:

Traceback (most recent call last):
File "C:/Users/user1/Desktop/Py/AgentsStatus/testGraph.py", line 57, in <module>
    plt.plot(dateCol,okCol,linewidth=5)
File "C:\Python34\lib\site-packages\matplotlib\pyplot.py", line 3154, in plot
    ret = ax.plot(*args, **kwargs)
File "C:\Python34\lib\site-packages\matplotlib\__init__.py", line 1812, in inner
    return func(ax, *args, **kwargs)
File "C:\Python34\lib\site-packages\matplotlib\axes\_axes.py", line 1425, in plot
    self.add_line(line)
File "C:\Python34\lib\site-packages\matplotlib\axes\_base.py", line 1708, in add_line
    self._update_line_limits(line)
File "C:\Python34\lib\site-packages\matplotlib\axes\_base.py", line 1730, in _update_line_limits
    path = line.get_path()
File "C:\Python34\lib\site-packages\matplotlib\lines.py", line 925, in get_path
    self.recache()
File "C:\Python34\lib\site-packages\matplotlib\lines.py", line 612, in recache
    x = np.asarray(xconv, np.float_)
File "C:\Python34\lib\site-packages\numpy\core\numeric.py", line 482, in asarray
    return array(a, dtype, copy=False, order=order)
ValueError: could not convert string to float: '11-04-2016'

CSV contains:

11-04-2016;37180;6;23852
18-04-2016;37341;9;24105
25-04-2016;37075;18;23788

My code is:

import csv
import matplotlib.pyplot as plt
import os

path = 'C:\\Users\\user1\\Desktop\\Py\\AgentsStatus\\data.csv'

with open (path) as csvfile:
    readCSV = csv.reader(csvfile, delimiter=';')

    dateCol = [] # date list

    for row in readCSV:
        if row:
            date0 = row[0]
            dateCol.append(date0)

with open (path) as csvfile:
    readCSV = csv.reader(csvfile, delimiter=';')

    okCol = [] # all agents list

    for row in readCSV:
        if row:
            ok0 = row[1]
            okCol.append(ok0)


with open (path) as csvfile:
    readCSV = csv.reader(csvfile, delimiter=';')

    heaCol = [] # healthy list




from matplotlib import pyplot as plt
from matplotlib import style

style.use('ggplot')


# can plot specifically, after just showing the defaults:
plt.plot(dateCol,okCol,linewidth=5)
plt.plot(dateCol,heaCol,linewidth=5)

plt.title('Epic Info')
plt.ylabel('Y axis')
plt.xlabel('X axis')

plt.show()

My goal is to create something like below:

Could you give me please some tips of what am I doing wrong? I think my problem mitght be that I am not setting the List dateCol as the Index for the graph (to not plot it). Could you please help me on that?

Thanks a lot.

I am getting an error related to the date column - What is the error? — That1Guy
– That1Guy, Commented Jul 13, 2016 at 14:16
Hello, its ValueError: could not convert string to float: '11-04-2016' — Gonzalo
– Gonzalo, Commented Jul 13, 2016 at 14:17
That's an important piece of information - include the entire traceback in your question. — That1Guy
– That1Guy, Commented Jul 13, 2016 at 14:19
Your problem may go a little deeper than just that error. Have you looked at this recipe? matplotlib.org/examples/api/date_demo.html — Vince W.
– Vince W., Commented Jul 13, 2016 at 14:21

chthonicdaemon · Accepted Answer · 2016-07-13 17:01:04Z

2

For stuff like this Pandas is unbeatable:

import pandas
import matplotlib.pyplot as plt

df = pandas.read_csv('sampledata.csv', delimiter=';', 
                     index_col=0, 
                     parse_dates=[0], dayfirst=True, 
                     names=['date','a','b','c'])
df.plot()

plt.savefig('sampledata.png')

Results in

answered Jul 13, 2016 at 17:01

chthonicdaemon

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2 Comments

Gonzalo Over a year ago

Thank you. It's what I was looking for. Just one question, where can I find information to configure for example colors of lines, write dates in vertical (for bigger sets of data), etc..?

chthonicdaemon Over a year ago

The docs are pretty good.

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