How to plot data, time on x-axis not datetime

Question

   id        timestamp          energy
0   a   2012-03-18 10:00:00     0.034
1   b   2012-03-20 10:30:00     0.052
2   c   2013-05-29 11:00:00     0.055
3   d   2014-06-20 01:00:00     0.028
4   a   2015-02-10 12:00:00     0.069

I want to plot these data like below. just time on x-axis, not date nor datetime.

because I want to see the values per each hour.

https://i.sstatic.net/u73eJ.png

but this code plot like this.

plt.plot(df['timestamp'], df['energy'])

https://i.sstatic.net/yd6NL.png

I tried some codes but they just format the X data hide date part and plot like second graph.

+ df['timestamp'] is datetime type.

what should I do? Thanks.

try replacing df['timestamp'] with df['timestamp'].dt.time — gbruenjes
– gbruenjes, Commented May 6, 2020 at 7:37

Jose Vu · Accepted Answer · 2020-05-13 02:08:21Z

0

you can convert your datetime into time, if your df["timestamp"] is already in datetime format then

df["time"] = df["timestamp"].map(lambda x: x.time())
plt.plot(df['time'], df['energy'])

if df["timestamp"] is of type string then you can add one more line in front as df["timestamp"] = pd.to_datetime(df["timestamp"])

Update: look like matplotlib does not accept time types, just convert to string

df["time"] = df["timestamp"].map(lambda x: x.strftime("%H:%M"))
plt.scatter(df['time'], df['energy'])

edited May 13, 2020 at 2:08

answered May 6, 2020 at 7:43

Jose Vu

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2 Comments

SoHyeonAn Over a year ago

I already tried converting date time to time df['timestamp'] = pd.to_datetime(df['timestamp]) df['time] = df['timestamp].dt.time like this. but when I plot, TypeError : float() argument must be a string or a number, not 'datetime.time' occurred even I tested with your answer code.

Jose Vu Over a year ago

look like matplotlib does not allow "time" type, you can try convert df["time"] to string type by df["time"] = df["timestamp"].map(lambda x: x.strftime("%H:%M")) and try to plot again plt.scatter(df['time'], df['energy'])

shree ram · Accepted Answer · 2020-05-06 08:15:09Z

0

First check, if type of df["timestamp"] is in datetime format. if not

import pandas as pd  
time = pd.to_datetime(df["timestamp"])
print(type(time))

Then,

import matplotlib.pyplot as plt
values = df['energy']
plt.plot_date(dates , values )
plt.xticks(rotation=45)
plt.show()

answered May 6, 2020 at 8:15

shree ram

1

1 Comment

SoHyeonAn Over a year ago

df['timestamp'] is already datetime type. and It still plot like second graph.

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