Iterating over DataFrame columns to make Matplotlib line plot

Question

So, I know similar questions have been posted, but nothing has worked for my particular case yet. I know it can be done with the Pandas plot function, but these lines need to be on a Matplotlib figure so they can be plotted with scatters and other things...

I have a DataFrame like this:

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

lines = pd.DataFrame(columns=list('ABC'))
lines.columns = ['T', 'Line1', 'Line2']
lines['T'] = np.arange(0,100,0.1)
lines['Line1'] = np.cos(lines['T']) + 30
lines['Line2'] = np.sin(lines['T']) + 13

And I want to make a plot with 2 separate lines that share the same X axis. I can do it like this:

plt.figure()
plt.plot(lines['T'], lines['Line1'])
plt.plot(lines['T'], lines['Line2'])
plt.show()

Which gives me:

But, I'd like to do it via loop. Sorry if this has been answered somewhere else, but I couldn't find it. Any help would be appreciated! Thanks.

@QuangHoang this should be the answer. If you write it I will delete mine and upvote you — Itay
– Itay, Commented Aug 21, 2019 at 14:52
@KartikeyaSharma, it seems Cody does want the rest of the columns plotted according to his comment. That's why he wants a loop - so he doesn't have to keep adding .plot calls when new columns are added — Omer Tuchfeld
– Omer Tuchfeld, Commented Aug 21, 2019 at 14:56

Itay · Accepted Answer · 2019-08-21 14:49:38Z

1

By using the columns property of the dataframe.

plt.plot(lines[lines.columns[0]], lines[lines.columns[1:]])

Or simply as Quang Hoang suggested in a comment:

lines.plot(x='T')

answered Aug 21, 2019 at 14:49

Itay

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Omer Tuchfeld · Accepted Answer · 2019-08-21 14:50:38Z

0

If you insist on using a loop then you can do something like this:

for column in lines:
    if column != 'T':
        plt.plot(lines['T'], lines[column])

answered Aug 21, 2019 at 14:50

Omer Tuchfeld

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1 Comment

Omer Tuchfeld Over a year ago

Good to hear, although I suggest @QuangHoang's comment as a better solution, it's much more simpler and readable (even though it doesn't include iteration as originally requested in your question)

Ted · Accepted Answer · 2019-08-21 14:48:21Z

0

line_cols = ["Line1", "Line2"]

plt.figure()
for l in line_cols:
    plt.plot(lines['T'], lines[l])
plt.show()

answered Aug 21, 2019 at 14:48

Ted

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