python plotting a histogram from dataframe column

Question

Looking to plot a histogram emanating from a dataframe, I seem to lack in transforming to a right object type that matplotlib can deal with. Here are some failed attempts. How do I fix it up?

And more generally, how do you typically salvage something like that?

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

filter(lambda v: v > 0, df['foo_col']).hist(bins=10)

---> 10 filter(lambda v: v > 0, df['foo_col']).hist(bins=100) AttributeError: 'filter' object has no attribute 'hist'

hist(filter(lambda v: v > 0, df['foo_col']), bins=100)

---> 10 hist(filter(lambda v: v > 0, df['foo_col']), bins=100) TypeError: 'Series' object is not callable

I'm confused about what you're trying to do. You want to plot a histogram for all values > 0? — roganjosh
– roganjosh, Commented May 26, 2018 at 7:28

roganjosh · Accepted Answer · 2018-05-26 07:45:29Z

2

By all accounts, filter is lucky to be part of the standard library. IIUC, you just want to filter your dataframe to plot a histogram of values > 0. Pandas has its own syntax for that:

import numpy as np
import pandas as pd

import matplotlib.pyplot as plt

data = np.random.randint(-50, 1000, 10000)

df = pd.DataFrame({'some_data': data})

df[df['some_data'] >= 0].hist(bins=100)
plt.show()

Note that this will run much faster than python builtins could ever hope to (it doesn't make much difference in my trivial example, but it will with bigger datasets). It's important to use pandas methods with dataframes wherever possible because, in many cases, the calculation will be vectorized and run in highly optimised C/C++ code.

edited May 26, 2018 at 7:45

answered May 26, 2018 at 7:38

roganjosh

13.3k4 gold badges33 silver badges53 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

python plotting a histogram from dataframe column

1 Answer 1

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related