How to remove Outliers in Python?

Question

I want to remove outliers from my dataset “train” for which purpose I’ve decided to use z-score or IQR.

I’m running Jupyter notebook on Microsoft Python Client for SQL Server.

I’ve tried for z-score:

from scipy import stats
train[(np.abs(stats.zscore(train)) < 3).all(axis=1)]

for IQR:

Q1 = train.quantile(0.02)
Q3 = train.quantile(0.98)
IQR = Q3 - Q1
train = train[~((train < (Q1 - 1.5 * IQR)) |(train > (Q3 + 1.5 * 
IQR))).any(axis=1)]

…which returns…

for z-score:

TypeError: unsupported operand type(s) for /: ‘str’ and ‘int’

for IQR:

TypeError: unorderable types: str() < float()

My train dataset looks like:

# Number of each type of column
print('Training data shape: ', train.shape)
train.dtypes.value_counts()

Training data shape: (300000, 111) int32 66 float64 30 object 15 dtype: int64

Help would be appreciated.

Asked By: Stanislav Jirák

||

Source

Answer 1

You’re having trouble with your code because you’re trying to calculate zscore on categorical columns.

To avoid this, you should first separate your train into parts with numerical and categorical features:

num_train = train.select_dtypes(include=["number"])
cat_train = train.select_dtypes(exclude=["number"])

and only after that calculate index of rows to keep:

idx = np.all(stats.zscore(num_train) < 3, axis=1)

and finally add the two pieces together:

train_cleaned = pd.concat([num_train.loc[idx], cat_train.loc[idx]], axis=1)

For IQR part:

Q1 = num_train.quantile(0.02)
Q3 = num_train.quantile(0.98)
IQR = Q3 - Q1
idx = ~((num_train < (Q1 - 1.5 * IQR)) | (num_train > (Q3 + 1.5 * IQR))).any(axis=1)
train_cleaned = pd.concat([num_train.loc[idx], cat_train.loc[idx]], axis=1)

Please let us know if you have any further questions.

PS

As well, you might consider one more approach for dealing with outliers with pandas.DataFrame.clip, which will clip outliers on a case-by-case basis instead of dropping a row altogether.

Answered By: Sergey Bushmanov

Answer 2

you can use autooptimizer module.

pip install autooptimizer

from autooptimizer.process import outlier_removal

Answered By: mohamadreza barghi

How to remove Outliers in Python?

Question:

Answers: