Methods to Calculate Standard Deviation
The standard deviation is a metric that measures how widely dispersed data points are. It calculates the deviation of each data point from the mean value of the dataset.
Typically, pandas provides three methods to calculate the standard deviation: std(), describe(), and apply(). The most commonly used method is the std() function.
Let’s see how it works in the following examples.
Standard Deviation of One Column
Suppose you have a dataset with a single numerical column, and you want to compute its standard deviation using pandas. You can use the std() function to calculate the standard deviation of this column.
For example, consider the following dataset:
df = pd.DataFrame({'height':[173, 168, 189, 161, 180]})
You can calculate the standard deviation of this dataset using the following code:
df['height'].std()
This code returns the standard deviation of the ‘height’ column. The output is:
8.38686870087773
This value tells us that the height values in this dataset are dispersed roughly 8.39 units from their mean.
Standard Deviation of Multiple Columns
Now, let’s consider a dataset with multiple numerical columns. You may want to compute the standard deviation of each column independently to understand the range of values in each column.
Suppose you have the following dataset:
df = pd.DataFrame({'age':[23, 25, 29, 33, 45], 'salary':[45000, 55000, 65000, 75000, 85000]})
To calculate the standard deviation of each column, you can use the following code:
df_std = df.std()
print(df_std)
The output of this code will return the standard deviation of each column:
age 8.024924
salary 1613.733167
dtype: float64
This output demonstrates that the standard deviation of the ‘age’ column is 8.02 units, while that of the ‘salary’ column is 1613.73 units.
Standard Deviation of All Numeric Columns
In some cases, you might have a dataset with multiple columns, but you only want to calculate the standard deviation of numeric columns. You can do this using the describe() function.
Consider the following dataset:
df = pd.DataFrame({'name':['Tom', 'Jack', 'Mary'],
'age':[23, 26, 28],
'height':[167, 174, 176],
'salary':[45000, 55000, 65000]})
To calculate the standard deviation of all numerical columns, you can run the following code:
df_std = df.describe(percentiles=[], include='number').loc['std']
print(df_std)
The output of this code will return the standard deviation of all numerical columns:
age 2.081666
height 4.320494
salary 10196.606774
Name: std, dtype: float64
In this dataset, the ‘age’ and ‘height’ columns have standard deviations of 2.08 and 4.32 units, respectively, while the salary column has a standard deviation of 10,196.61 units.
Additional Resources
Pandas provides a broad range of functions, beyond those mentioned in this article, that users can utilize to manipulate DataFrame objects. Understanding these functions is essential to performing in-depth data analysis with pandas.
Here are some excellent resources that provide detailed tutorials on pandas operations:
- Official Pandas Documentation: pandas.pydata.org/docs/
- “10 Minutes to pandas” Tutorial: pandas.pydata.org/pandas-docs/stable/user_guide/10min.html
- DataCamp Tutorial: www.datacamp.com/community/tutorials/pandas-tutorial-dataframe-python
Conclusion
In this article, we explored how to calculate the standard deviation of pandas DataFrame columns. We used the std(), describe(), and apply() functions to calculate the standard deviation of one or multiple columns and provided a list of resources for users looking to expand upon their current knowledge of pandas.
Employing proper statistical analysis within pandas is vital to developing high-quality insights and models that can help you draw meaningful conclusions from data. Armed with the knowledge we’ve provided, you can begin to leverage pandas analysis and data manipulation to fully understand the data contained in your datasets.
In summary, this article highlights the importance of standard deviation in the analysis of data and how to calculate standard deviation in pandas DataFrames efficiently. We demonstrated how to use the std() function to compute standard deviation of one or many columns and how to calculate the standard deviation of all numeric columns using the describe() function.
Additionally, we provided resources for readers to learn more about pandas operations. Understanding how to calculate standard deviation is crucial in discovering trends in numerical data, and it is a fundamental component of statistical analysis.
With the information provided in this article, individuals can elevate their data analysis skills and employ proper statistical analysis within pandas to yield meaningful insights and models from their datasets.