Database graph does not appear python matplotlib

Question

Database graph does not appear python matplotlib

Navigation

#1 by (5 votes)
#2 by (0 votes)

1

The outline of the graph appears, but empty, with no data.

import sqlite3
import matplotlib.pyplot as plt 
import matplotlib.dates as mdates


connection = sqlite3.connect('escola.db')
c = connection.cursor()

sql= "SELECT DATE_EXTRACTION, NOTAS FROM ESCOLA where turma_id='T1'"

x = []
y = []

conversor = mdates.strpdate2num('%m-%d-%Y %H:%M:%S') 


def read_data (wordUsed):
    for row in c.execute(sql):
        x.append(conversor(row[1]))
        y.append(row[2])

fig = plt.figure()
ax1 = fig.add_subplot(1, 1, 1, axisbg= 'white')
plt.ylim(0,50000)
plt.xlim(2014, 2015)
plt.plot_date(x, y, fmt='b-', label= 'values', linewidth=2)
plt.legend(['values'])
plt.grid(True)
plt.show()

Message:

136: MatplotlibDeprecationWarning: The axisbg attribute was deprecated in version 2.0. Use facecolor instead.
  warnings.warn(message, mplDeprecation, stacklevel=1)

sqlite python matplotlib

asked by anonymous 05.03.2017 / 22:08

2 answers

0

The error message is very clear, the axisbg function has been deprecated in version 2.0 and has been replaced with facecolor try changing this line:

ax1 = fig.add_subplot(1, 1, 1, axisbg= 'white')

For this

ax1 = fig.add_subplot(1, 1, 1, facecolor= 'white')

05.03.2017 / 22:19

Code stacking and unstacking a stack Hide the destination URL

score 5 · Accepted Answer

Your code has some potential problems:

Data variables x and y are only populated within the read_data function, which is never called . So the data is empty and the graph shows nothing. Run the function before creating the chart!

Even if the function was called, it handles local variables, not the global variables x and y . Declare them again within the function as global, or else (I think it best) make the function return its values.

Potentially stressing the limits of the x and y axes can also cause no data to be displayed. When so, comment on the lines with plt.xlim and plt.ylim just to be sure.

Since you did not bother to make a Minimum, Complete and Verifiable Example that could be tested (I do not have how to rotate your code, since I do not have your database and I do not even know what data is expected), I have prepared a test that takes the quotations from Yahoo. The data source is different, but the output of the chart is exactly the same. See the code:

import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import datetime

from matplotlib.finance import quotes_historical_yahoo_ochl
from matplotlib.dates import YearLocator, MonthLocator, DateFormatter

x = []
y = []

def read_data():

    # Apenas para teste
    # -------------------

    date1 = datetime.date(1995, 1, 1)
    date2 = datetime.date(2004, 4, 12)

    quotes = quotes_historical_yahoo_ochl('INTC', date1, date2)
    if len(quotes) == 0:
        raise SystemExit

    global x # CORREÇÃO: Declare x e y como globais!
    global y

    x = [q[0] for q in quotes]
    y = [q[1] for q in quotes]

read_data() # CORREÇÃO: Chame a função!!

fig = plt.figure()
ax1 = fig.add_subplot(1, 1, 1, axisbg= 'white')
#plt.ylim(0,50000) # DEPURAÇÃO: Comente para ver se isso também não contribui para o "problema"
#plt.xlim(2014, 2015)
plt.plot_date(x, y, fmt='b-', label= 'values', linewidth=2)
plt.legend(['values'])
plt.grid(True)
plt.show()

Result: