Advent of 2020, Day 12 – Using Azure Databricks Notebooks with Python Language for data analytics

This article is originally published at https://tomaztsql.wordpress.com

Series of Azure Databricks posts:

• Dec 01: What is Azure Databricks
• Dec 02: How to get started with Azure Databricks
• Dec 03: Getting to know the workspace and Azure Databricks platform
• Dec 04: Creating your first Azure Databricks cluster
• Dec 05: Understanding Azure Databricks cluster architecture, workers, drivers and jobs
• Dec 06: Importing and storing data to Azure Databricks
• Dec 07: Starting with Databricks notebooks and loading data to DBFS
• Dec 08: Using Databricks CLI and DBFS CLI for file upload
• Dec 09: Connect to Azure Blob storage using Notebooks in Azure Databricks
• Dec 10: Using Azure Databricks Notebooks with SQL for Data engineering tasks
• Dec 11: Using Azure Databricks Notebooks with R Language for data analytics

We looked into SQL and R language and how to get some basic data preparation done. Today we will look into Python and how to go about data analytics.

Using data frames and getting data from SQL and DBFS

Create a new notebook with Name: Day12_Py_Analytics and Language: Python and connect notebook to a cluster we have created on Day 4. And let’s go and add some data from FileStore and use data that we uploaded in Day 6.

csv_df = spark.read.csv("/FileStore/Day6Data_dbfs.csv", header="True")
display(csv_df)

We can also import data from SQL Table into data frame by simply writing an SQL statement.

#from pyspark.sql.functions import explode
from pyspark.sql import *
import pandas as pd

display(sql("select * from day10.temperature"))

Besides displaying dataset, you can store a result of a query to a variable and use it later.

#for display
display(sql("select * from day10.temperature"))

#to save to variable
df = sql("select * from day10.temperature")

Let’s get now some data from Databricks sample data (that is available to anybody). So you can insert data from dbfs store and use the sample datasets as well, by using Python Pandas.

import pandas as pd

dfcovid = pd.read_csv("/dbfs/databricks-datasets/COVID/covid-19-data/us-states.csv")
dfcovid.head()

and now let’s scatter plot some number of cases and deaths per states and use the following Python code that can be simply used in Azure Databricks.

# Filter to 2020-12-01 on first of december
df_12_01 = dfcovid[dfcovid["date"] == "2020-12-01"] 

ax = df_12_01.plot(x="cases", y="deaths", kind="scatter", 
                   figsize=(12,8), s=100, title="Deaths vs Cases on 2020-12-01 - All States")

df_12_01[["cases", "deaths", "state"]].apply(lambda row: ax.text(*row), axis=1);

And now let’s compare only couple of these extreme states (New York, Texas, California and Florida). And create a subset for only these four states:

df_ny_cal_tex_flor = dfcovid[(dfcovid["state"] == "New York") | (dfcovid["state"] == "California") | (dfcovid["state"] == "Florida") | (dfcovid["state"] == "Texas")]

And now to create an index for the plot of deaths over time

df_ny_cal_tex_flor = df_ny_cal_tex_flor.pivot(index='date', columns='state', values='deaths').fillna(0)
df_ny_cal_tex_flor

and now plot this data using this dataset:

df_ny_cal_tex_flor.plot.line(title="Deaths 2020-01-25 to 2020-12-10 - CA, NY, TX, FL", figsize=(12,8))

And now for a simple regression analysis, we will split data from test and train. Since the first and second wave we will need to thing how to split the data. Let’s split it until mid of November and after mid of November.

train_df = dfcovid[(dfcovid["date"] >= "2020-07-01") & (dfcovid["date"] <= "2020-11-15")]
test_df = dfcovid[dfcovid["date"] > "2020-11-16"]

X_train = train_df[["cases"]]
y_train = train_df["deaths"]

X_test = test_df[["cases"]]
y_test = test_df["deaths"]

We will use scikit-learn to do simple linear regression.

from sklearn.linear_model import LinearRegression

lr = LinearRegression().fit(X_train, y_train)
print(f"num_deaths = {lr.intercept_:.4f} + {lr.coef_[0]:.4f}*cases")

So if we have no cases, then there should be no deaths caused by COVID-19; this gives us a base line and assume that let’s set the intercept to be 0.

lr = LinearRegression(fit_intercept=False).fit(X_train, y_train)
print(f"num_deaths = {lr.coef_[0]:.4f}*cases")

This model imposes that there is a 2.68% mortality rate in our dataset. But we know that some states have higher mortality rates and that linear model is absolutely not ideal for that, but it is just to showcase for using Python in Databricks.

Tomorrow we will check and explore how to use Python Koalas to do data engineering, so stay tuned.

Complete set of code and Notebooks will be available at the Github repository.

Happy Coding and Stay Healthy!

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