# How to Calculate Deciles in Python

In statistics, a decile is a method of splitting up a set of observations into 10 equally large subsections. Deciles are often used in data analysis for understanding the distribution of data. This guide will walk you through how to calculate deciles using Python, a popular programming language used for data analysis and manipulation.

### Method 1: Using Pandas qcut Function

One way to calculate deciles in Python is to use the qcut function from the Pandas library, which divides data into equal-sized bins. In our case, the number of bins will be 10 for deciles.

Let’s consider a simple example where we have a Pandas DataFrame with some randomly generated data:

import pandas as pd
import numpy as np

# Create a DataFrame with random data
df = pd.DataFrame({
'value': np.random.randint(1, 100, 200)
})

# Calculate deciles
df['decile'] = pd.qcut(df['value'], 10, labels=False)

# Print the first few rows


Here, pd.qcut(df['value'], 10, labels=False) divides the value column into 10 bins. labels=False means that it returns the bin number (from 0 to 9) instead of bin ranges.

### Method 2: Using Pandas quantile Function

You can also calculate the decile boundaries using the quantile function in Pandas. The quantile function returns the value at a given quantile (i.e., percentile).

Here’s an example:

import pandas as pd
import numpy as np

# Create a DataFrame with random data
df = pd.DataFrame({
'value': np.random.randint(1, 100, 200)
})

# Calculate deciles
deciles = df['value'].quantile([.1, .2, .3, .4, .5, .6, .7, .8, .9])

print(deciles)


In this example, df['value'].quantile([.1, .2, .3, .4, .5, .6, .7, .8, .9]) calculates the value at each decile from the 10th percentile to the 90th percentile.

### Method 3: Using NumPy percentile Function

You can also use the percentile function from NumPy to compute deciles. This function works similarly to the quantile function in Pandas.

Here’s how you can do it:

import numpy as np

# Create a numpy array with random data
data = np.random.randint(1, 100, 200)

# Calculate deciles
deciles = [np.percentile(data, i*10) for i in range(1, 10)]

print(deciles)

Here, np.percentile(data, i*10) calculates the value at each decile from the 10th percentile to the 90th percentile.

### Conclusion

In this guide, we’ve discussed three different methods to calculate deciles in Python. These methods provide a convenient way to understand and analyze the distribution of your data. It’s important to note that the actual decile values may vary slightly between the methods due to different interpolation methods used in the underlying algorithms. Therefore, you should choose the method that best suits your particular use case and data set.

Remember that understanding your data distribution is crucial for effective data analysis and predictive modeling. Deciles, along with other summary statistics like mean, median, and quartiles, are valuable tools to achieve that understanding.