CODEWITHSUNDEEP
pythonpandasnumpymatplotlib
Bethany Jade
Bethany Jade

Reputation: 43

Python Date Not Plotting Properly

I was wondering why the x-axis plots the dates wrong, it begins at the 05/02 when it should start at the 30/01, and I'm not sure where it is I went wrong.

import pandas as pd
import matplotlib.pyplot as plt
import numpy as np

cols = ['Time','Water Usage']
A = pd.read_csv("CSVFile", names=cols, parse_dates=[0])

plt.ylabel = "Time"
plt.xlabel = "Water Usage"
A.plot(x='Time',y='Water Usage')
plt.show()

The file is in the format

Date+Time  |  Usage

30/01/2018  | 50091

05/02/2018 |  50890

so ideally it should plot the 30/01 first followed by the 05/02, whereas currently its doing the opposite.

Upvotes: 0

Views: 1447

Answers (2)

t.novaes
t.novaes

Reputation: 126

To make sure your program plots the x-values chronologically, you should convert the Date+Time column into a datetime object. I see you used parse_dates in your read_csvcall, but the docs say it might not be 100% effective:

If a column or index cannot be represented as an array of datetimes, say because of an unparseable value or a mixture of timezones, the column or index will be returned unaltered as an object data type. For non-standard datetime parsing, use pd.to_datetime after pd.read_csv. To parse an index or column with a mixture of timezones, specify date_parser to be a partially-applied pandas.to_datetime() with utc=True. See Parsing a CSV with mixed timezones for more.

So I would try the following (to_datetime):

A['Time'] = pd.to_datetime(A['Time'])
A.sort_values(by='Time', inplace = True)

I hope it helps!

Upvotes: 2

NYC Coder
NYC Coder

Reputation: 7604

Just made a few changes to your code, mainly pd.to_datetime and it works fine:

cols = ['Time','Water Usage']
df = pd.read_csv('test.csv', sep='|')
df.columns = cols
df['Time'] = pd.to_datetime(df['Time'], format='%d/%m/%Y')
plt.ylabel = "Time"
plt.xlabel = "Water Usage"
df.plot(x='Time',y='Water Usage')
plt.show()

Upvotes: 0

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