Data Homogenization | Dagster Glossary

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Data Homogenization

Make data uniform, consistent, and comparable.

Data homogenization definition

Data homogenization is the process of making data uniform, consistent, and comparable. As data sources multiply and diversify, data can come in various formats, structures, and quality. When we talk about homogenizing data, we're talking about transforming and preparing this diverse data in a way that it becomes coherent and can be used seamlessly across applications, analyses, or systems.

Data homogenization is crucial in scenarios like data integration, business intelligence, analytics, and more, where coherent and consistent data is a requirement for accurate insights or smooth functioning of applications.

The many steps of data homogenization

Here's a breakdown of what this process might involve:

  1. Standardization: This is about making sure data adheres to a common standard. For instance, date values from one system might be in the format MM-DD-YYYY while another uses YYYY-MM-DD. Standardizing would involve picking one format and converting all dates to that format. See entry for standardization

  2. Normalization: This is about scaling numerical data to fall within a specific range. For instance, one system might represent a percentage as a value between 0 and 1 (like 0.85) while another represents it between 0 and 100 (like 85). Normalizing would involve converting all these values to a chosen range. See entry for normalization.

  3. Data Cleansing: This involves identifying and correcting (or removing) errors and inconsistencies in data to improve its quality. This could involve handling missing data, correcting typos or inaccuracies, and more. See entry for cleanse.

  4. Schema Mapping: If you're integrating data from multiple databases, each with its schema, you might need to map fields between them. For example, one database might have a field called "mobilenumber", and another has "cell_phone". Homogenization would involve deciding on a consistent naming convention and structure. See entry for schema mapping_

  5. Encoding and Categorization: Converting categorical data into a common format or encoding, like one-hot encoding, label encoding, etc. See entry for encode.

  6. Addressing Variability: Sometimes data from different sources might refer to similar things but have slight variability. For instance, company names could be abbreviated in some systems and spelled out in others. Part of homogenization could involve making these consistent. See entry for integration.

  7. Time Series Alignment: If you're dealing with time series data from different sources, they might have different granularities or time zones. Homogenization might involve resampling, aligning, and converting time zones to get consistent time series data. See entry for time series analysis.

Example of data homogenization in Python

Let's look at a scenario where you have to integrate sales data from two e-commerce platforms. Each platform provides data with various inconsistencies. We'll deal with:

  1. Different data formats
  2. Product categorization differences
  3. Currency conversions
  4. Data anomalies like outliers and missing values

We'll still use the pandas library and also numpy for some numerical operations.

import pandas as pd
import numpy as np

# Sample data
data1 = {
    'Date': ['01-01-2023', '01-02-2023', '01-03-2023', '01-04-2023'],
    'Product': ['Smartphone', 'Laptop', 'Tablet', 'Laptop'],
    'Category': ['Electronics', 'Computers', 'Electronics', 'Computers'],
    'Sales': [100, 200, 150, np.nan],
    'Currency': ['USD', 'USD', 'USD', 'USD']
}

data2 = {
    'Date': ['2023-01-01', '2023-01-02', '2023-01-03', '2023-01-04'],
    'Product': ['SPhone', 'Lap', 'Tab', 'Desk'],
    'Category': ['Mobile', 'Laptop', 'Tablet', 'Computer'],
    'Sales': [120, 2500, 160, -5], # Sales in a different currency & has an outlier
    'Currency': ['EUR', 'EUR', 'EUR', 'EUR']
}

df1 = pd.DataFrame(data1)
df2 = pd.DataFrame(data2)

# Convert date format in df2 to match df1
df2['Date'] = pd.to_datetime(df2['Date']).dt.strftime('%m-%d-%Y')

# Standardize product names using a mapping dictionary
product_map = {
    'SPhone': 'Smartphone',
    'Lap': 'Laptop',
    'Tab': 'Tablet',
    'Desk': 'Desktop'
}
df2['Product'] = df2['Product'].map(product_map)

# Map categories
category_map = {
    'Mobile': 'Electronics',
    'Laptop': 'Computers',
    'Tablet': 'Electronics',
    'Computer': 'Computers'
}
df2['Category'] = df2['Category'].map(category_map)

# Handling currency conversion
# Let's assume 1 EUR = 1.1 USD for simplicity
currency_conversion = {
    'EUR': 1.1
}
df2['Sales'] = df2.apply(lambda row: row['Sales'] * currency_conversion[row['Currency']] if row['Currency'] in currency_conversion else row['Sales'], axis=1)
df2['Currency'] = 'USD'

# Handle missing values in df1 by forward filling for simplicity
df1['Sales'].fillna(method='ffill', inplace=True)

# Handle outliers (negative sales, which is an anomaly)
df2['Sales'] = df2['Sales'].apply(lambda x: np.nan if x < 0 else x)
df2['Sales'].fillna(method='ffill', inplace=True) # forward fill for simplicity

# Merge dataframes
combined_data = pd.concat([df1, df2]).reset_index(drop=True)

print(combined_data)

In this example:

  1. We've addressed different date formats.
  2. Standardized product names and categories.
  3. Converted EUR to USD.
  4. Handled missing values using forward fill.
  5. Managed sales anomalies by replacing them with NaN and then using forward fill.

Try running this code on your own machine and you will see this result - a homogenized dataset:

         Date     Product     Category   Sales Currency
0  01-01-2023  Smartphone  Electronics   100.0      USD
1  01-02-2023      Laptop    Computers   200.0      USD
2  01-03-2023      Tablet  Electronics   150.0      USD
3  01-04-2023      Laptop    Computers   150.0      USD
4  01-01-2023  Smartphone  Electronics   132.0      USD
5  01-02-2023      Laptop    Computers  2750.0      USD
6  01-03-2023      Tablet  Electronics   176.0      USD
7  01-04-2023     Desktop    Computers   176.0      USD

In a more real-world setting, you might leverage external APIs for up-to-date currency conversion rates, use sophisticated imputation methods for missing values, and perhaps integrate statistical methods or machine learning models to handle anomalies more intelligently.


Other data engineering terms related to
Data Transformation:
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Align

Aligning data can mean one of three things: aligning datasets, meeting business rules, or arranging data elements in memory.
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Clean or Cleanse

Remove invalid or inconsistent data values, such as empty fields or outliers.
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Cluster

Group data points based on similarities or patterns to facilitate analysis and modeling.
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Curate

Select, organize, and annotate data to make it more useful for analysis and modeling.
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Denoise

Remove noise or artifacts from data to improve its accuracy and quality.
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Denormalize

Optimize data for faster read access by reducing the number of joins needed to retrieve related data.
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Derive

Extracting, transforming, and generating new data from existing datasets.
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Discretize

Transform continuous data into discrete categories or bins to simplify analysis.
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ETL

Extract, transform, and load data between different systems.
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Encode

Convert categorical variables into numerical representations for ML algorithms.
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Filter

Extract a subset of data based on specific criteria or conditions.
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Fragment

Break data down into smaller chunks for storage and management purposes.
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Impute

Fill in missing data values with estimated or imputed values to facilitate analysis.
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Linearize

Transforming the relationship between variables to make datasets approximately linear.
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Munge

See 'wrangle'.
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Normalize

Standardize data values to facilitate comparison and analysis. Organize data into a consistent format.
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Reduce

Convert a large set of data into a smaller, more manageable form without significant loss of information.
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Reshape

Change the structure of data to better fit specific analysis or modeling requirements.
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Serialize

Convert data into a linear format for efficient storage and processing.
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Shred

Break down large datasets into smaller, more manageable pieces for easier processing and analysis.
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Skew

An imbalance in the distribution or representation of data.
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Split

Divide a dataset into training, validation, and testing sets for machine learning model training.
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Standardize

Transform data to a common unit or format to facilitate comparison and analysis.
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Tokenize

Convert data into tokens or smaller units to simplify analysis or processing.
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Transform

Convert data from one format or structure to another.
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Wrangle

Convert unstructured data into a structured format.
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