How can I plot two graphs using one dataframe in matplotlib?

Question

I want to plot two graphs out of one pandas dataframe(a), by overlapping them.

This is part of the dataframe(a).

                       Temperature
DateTime
2017-05-01 07:20:00    49.15
2017-05-01 07:19:00    49.14
2017-05-01 07:18:00    49.15
2017-05-01 07:17:00    49.14
2017-05-01 07:16:00    49.14
2017-05-01 07:15:00    49.15
2017-05-01 07:14:00    49.15
2017-05-01 07:13:00    49.15
2017-05-01 07:12:00    49.16
2017-05-01 07:11:00    49.17
2017-05-01 07:10:00    49.18
2017-05-01 07:09:00    49.16
2017-05-01 07:08:00    49.15
2017-05-01 07:07:00    49.15
2017-05-01 07:06:00    49.16
2017-05-01 07:05:00    49.19
2017-05-01 07:04:00    49.19
2017-05-01 07:03:00    49.20
2017-05-01 07:02:00    49.21
2017-05-01 07:01:00    49.15

Firstly, I want to plot this graph as a timeseries. Secondly, I want to plot points that meet a certain condition. For example, I want to plot each teperature that is the highest value within the range of +- 5 rows. The below shows a function that I made for this condition.

def HIGH(a, span):
    for m in range(span, len(a)-span):
        temp_df = a.iloc[m-span:m+span]

        if a.iloc[m] == pd.DataFrame.max(temp_df, axis=0):
            print(a.index.values[m])
            print(a.iloc[m])

>>> HIGH(a, 5)
2017-05-01T07:10:00.000000000
49.18

>>> matplotlib.pyplot.plot(a)
>>> matplotlib.pyplot.show()

shows the graph below, but how can I mark the point(with 'rx' option)?

ImportanceOfBeingErnest · Accepted Answer · 2017-05-18 11:16:31Z

You need to return the values from the HIGH function and plot them with a marker.

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


u = u"""DateTime;Temperature
2017-05-01 07:20:00;49.15
2017-05-01 07:19:00;49.14
2017-05-01 07:18:00;49.15
2017-05-01 07:17:00;49.14
2017-05-01 07:16:00;49.14
2017-05-01 07:15:00;49.15
2017-05-01 07:14:00;49.15
2017-05-01 07:13:00;49.15
2017-05-01 07:12:00;49.16
2017-05-01 07:11:00;49.17
2017-05-01 07:10:00;49.18
2017-05-01 07:09:00;49.16
2017-05-01 07:08:00;49.15
2017-05-01 07:07:00;49.15
2017-05-01 07:06:00;49.16
2017-05-01 07:05:00;49.19
2017-05-01 07:04:00;49.19
2017-05-01 07:03:00;49.20
2017-05-01 07:02:00;49.21
2017-05-01 07:01:00;49.15"""

data = io.StringIO(u)
df = pd.read_csv(data, sep=";", index_col=0)
df.index = pd.to_datetime(df.index)


def HIGH(a, span):
    x,y = [],[]
    for m in range(span, len(a)-span):
        temp_df = a.iloc[m-span:m+span]
        cur = float(pd.DataFrame.max(temp_df, axis=0))
        if float(a.iloc[m]) == cur:
            x.append( a.index.values[m] )
            y.append( float(a.iloc[m]) )
    return x,y

plt.plot(df)
x,y = HIGH(df,5)
plt.plot(x,y, marker="*", color="crimson", ls="", ms=15)
plt.show()

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How can I plot two graphs using one dataframe in matplotlib?

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