Plotting through a subset of data frame in Pandas using Matplotlib

Question

I have a Dataframe and I slice the Dataframe into three subsets. Each subset has 3 to 4 rows of data. After I slice the data frame into three subsets, I plot them using Matplotlib.

The problem I have is I am not able to create a plot where each subplot is plotted using sliced DataFrame. For example, in a group of three in a set, I have only one of the plots (last subplot) plotted where there is no data for the remaining two plots initial sets in a group. it looks like the 'r' value does not pass to 'r.plot' for all three subplots.

import pandas as pd
import matplotlib.pyplot as plt
import numpy as np
df = pd.DataFrame(np.random.randn(10, 4), columns=list('ABCD'))

df['key1'] = 0
df.key1.iloc[0:3] = 1
df.key1.iloc[3:7] = 2
df.key1.iloc[7:] = 3

df_grouped = df.groupby('key1')

for group_name, group_value in df_grouped:
     rows, columns = group_value.shape
     fig, axes = plt.subplots(rows, 1, sharex=True, sharey=True, figsize=(15,20))
    for i,r in group_value.iterrows():
        r = r[0:columns-1]
        r.plot(kind='bar', fill=False, log=False)

thanks for providing a reproduceable example with random data. however, I can't quite reproduce this because the rows variable is not defined within this example. can you please clarify the value of rows? — Max Power
– Max Power, Commented Jun 12, 2017 at 23:33
The rows are the values in the index A,B,C and D created by the random number generator. This code should produce an output with just one of the subplot filled in each subset. The first subset is made of 3 rows of data, the second set contains four rows and third set contains three rows of data. Each row of data has 4 values, with the index of a, b, c and d. — Suresh Raja
– Suresh Raja, Commented Jun 12, 2017 at 23:34
sorry I should have been more clear. you define your rows variable in this line: rows, columns = group_value.shape, which doesn't come until three lines after you try to use it with this line: fig, axes = plt.subplots(rows, 1, sharex=True, sharey=True, figsize=(15,20)). To get this code example to run, rows has to be defined before its used. That's the error I'm getting trying to run your code. — Max Power
– Max Power, Commented Jun 12, 2017 at 23:36
Yes you are right. It should be moved as you suggest. However, in my subplots only one of them are plotted. That is the issue I am trying to solve. Thanks. — Suresh Raja
– Suresh Raja, Commented Jun 12, 2017 at 23:39

Max Power · Accepted Answer · 2017-06-13 00:07:09Z

1

I think you might want what I call df_subset to be summarized in some way, but here's a way to plot each group in its own panel.

# Your Code Setting Up the Dataset
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

df = pd.DataFrame(np.random.randn(10, 4), columns=list('ABCD'))

df['key1'] = 0
df.key1.iloc[0:3] = 1
df.key1.iloc[3:7] = 2
df.key1.iloc[7:] = 3


# My Code to Plot in Three Panels
distinct_keys = df['key1'].unique()
fig, axes = plt.subplots(len(distinct_keys), 1, sharex=True, figsize=(3,5)) 

for i, key in enumerate(distinct_keys):
    df_subset = df[df.key1==key]

    # {maybe insert a line here to summarize df_subset somehow interesting?}

    # plot
    axes[i] = df_subset.plot(kind='bar', fill=False, log=False)

answered Jun 13, 2017 at 0:07

Max Power

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1 Comment

Suresh Raja Over a year ago

Thanks, this works in the test case. But my data set needs a bit of work. I will work on it and report back here shortly.

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