Step 1: Prepare the input dataset for ML modeling

The project is based on the Heart Failure Prediction Dataset.

This first notebook:

• Performs a quick exploratory analysis of the input dataset: it looks at the structure of the dataset and the distribution of the values in the different categorical and continuous columns.

• Uses the functions from the project Python library to clean & prepare the input dataset before Machine Learning modeling. We will first clean categorical and continuous columns, then split the dataset into a train set and a test set.

Finally, we will transform this notebook into a Python recipe in the project Flow that will output the new train and test datasets.

Tip: Project libraries allow you to build shared code repositories. They can be synchronized with an external Git repository.

0. Import packages

Make sure you’re using the correct code environment (see prerequisites)

To be sure, go to Kernel > Change kernel and choose py_quickstart

%pylab inline

Populating the interactive namespace from numpy and matplotlib

import dataiku
from dataiku import pandasutils as pdu
import pandas as pd
import matplotlib.pyplot as plt
import seaborn as sns
import math
from utils import data_processing
from sklearn.preprocessing import RobustScaler
from sklearn.model_selection import train_test_split

import warnings
warnings.filterwarnings('ignore')

1. Import the data

Let’s use the Dataiku Python API to import the input dataset. This piece of code allows retrieving data in the same manner, no matter where the dataset is stored (local filesystem, SQL database, Cloud data lakes, etc.)

dataset_heart_measures = dataiku.Dataset("heart_measures")
df = dataset_heart_measures.get_dataframe(limit=100000)

2. A quick audit of the dataset

2.1 Compute the shape of the dataset

print(f'The shape of the dataset is {df.shape}')

The shape of the dataset is (918, 12)

2.2 Look at a preview of the first rows of the dataset

df.head()

Export dataframe

	Age	Sex	ChestPainType	RestingBP	Cholesterol	FastingBS	RestingECG	MaxHR	ExerciseAngina	Oldpeak	ST_Slope	HeartDisease
0	40	M	ATA	140	289	0	Normal	172	N	0.0	Up	0
1	49	F	NAP	160	180	0	Normal	156	N	1.0	Flat	1
2	37	M	ATA	130	283	0	ST	98	N	0.0	Up	0
3	48	F	ASY	138	214	0	Normal	108	Y	1.5	Flat	1
4	54	M	NAP	150	195	0	Normal	122	N	0.0	Up	0

2.3 Inspect missing values & number of distinct values (cardinality) for each column

pdu.audit(df)

Export dataframe

	_a_variable	_b_data_type	_c_cardinality	_d_missings	_e_sample_values
0	Age	int64	50	0	[40, 49]
1	Sex	object	2	0	[M, F]
2	ChestPainType	object	4	0	[ATA, NAP]
3	RestingBP	int64	67	0	[140, 160]
4	Cholesterol	int64	222	0	[289, 180]
5	FastingBS	int64	2	0	[0, 1]
6	RestingECG	object	3	0	[Normal, ST]
7	MaxHR	int64	119	0	[172, 156]
8	ExerciseAngina	object	2	0	[N, Y]
9	Oldpeak	float64	53	0	[0.0, 1.0]
10	ST_Slope	object	3	0	[Up, Flat]
11	HeartDisease	int64	2	0	[0, 1]

3. Exploratory data analysis

3.1 Define categorical & continuous columns

categorical_cols = ['Sex','ChestPainType', 'FastingBS', 'RestingECG', 'ExerciseAngina', 'ST_Slope']
continuous_cols = ['Age', 'RestingBP', 'Cholesterol', 'MaxHR', 'Oldpeak']

3.2 Look at the distibution of continuous features

nb_cols=2
fig = plt.figure(figsize=(8,6))
fig.suptitle('Distribution of continuous features', fontsize=11)
gs = fig.add_gridspec(math.ceil(len(continuous_cols)/nb_cols),nb_cols)
gs.update(wspace=0.3, hspace=0.4)
for i, col in enumerate(continuous_cols):
    ax = fig.add_subplot(gs[math.floor(i/nb_cols),i%nb_cols])
    sns.histplot(x=df[col], ax=ax)

3.3 Look at the distribution of categorical columns

nb_cols=2
fig = plt.figure(figsize=(8,6))
fig.suptitle('Distribution of categorical features', fontsize=11)
gs = fig.add_gridspec(math.ceil(len(categorical_cols)/nb_cols),nb_cols)
gs.update(wspace=0.3, hspace=0.4)
for i, col in enumerate(categorical_cols):
    ax = fig.add_subplot(gs[math.floor(i/nb_cols),i%nb_cols])
    plot = sns.countplot(x=df[col], palette="colorblind")

3.4 Look at the distribution of target variable

target = "HeartDisease"
fig = plt.figure(figsize=(4,2.5))
fig.suptitle('Distribution of heart disease', fontsize=11, y=1.11)
plot = sns.countplot(x=df[target], palette="colorblind")

Tip: To ease collaboration, all the insights you create from Jupyter Notebooks can be shared with other users by publishing them on dashboards. See the documentation for more information.

4. Prepare data

4.1 Clean categorical columns

# Transform string values from categorical columns into int, using the functions from the project libraries
df_cleaned = data_processing.transform_heart_categorical_measures(df, "ChestPainType", "RestingECG",
                                                                  "ExerciseAngina", "ST_Slope", "Sex")

df_cleaned.head()

Export dataframe

	Age	Sex	ChestPainType	RestingBP	Cholesterol	FastingBS	RestingECG	MaxHR	ExerciseAngina	Oldpeak	ST_Slope	HeartDisease
0	40	0	2	140	289	0	0	172	0	0.0	2	0
1	49	1	3	160	180	0	0	156	0	1.0	1	1
2	37	0	2	130	283	0	1	98	0	0.0	2	0
3	48	1	4	138	214	0	0	108	1	1.5	1	1
4	54	0	3	150	195	0	0	122	0	0.0	2	0

4.2 Transform categorical columns into dummies

df_cleaned = pd.get_dummies(df_cleaned, columns = categorical_cols, drop_first = True)

print("Shape after dummies transformation: " + str(df_cleaned.shape))

Shape after dummies transformation: (918, 16)

4.3 Scale continuous columns

Let’s use the Scikit-Learn Robust Scaler to scale continuous features

scaler = RobustScaler()
df_cleaned[continuous_cols] = scaler.fit_transform(df_cleaned[continuous_cols])

5. Split the dataset into train and test

Let’s now split the dataset into a train set that will be used for experimenting and training the Machine Learning models and test set that will be used to evaluate the deployed model.

heart_measures_train_df, heart_measures_test_df = train_test_split(df_cleaned, test_size=0.2, stratify=df_cleaned.HeartDisease)

6. Next: use this notebook to create a new step in the project workflow

Now that our notebook is up and running, we can use it to create the first step of our pipeline in the Flow:

• Click on the + Create Recipe button at the top right of the screen.

• Select the Python recipe option.

• Choose the heart_measures dataset as the input dataset and create two output datasets: heart_measures_train and heart_measures_test.

• Click on the Create recipe button.

• At the end of the recipe script, replace the last four rows of code with:

heart_measures_train = dataiku.Dataset("heart_measures_train")
heart_measures_train.write_with_schema(heart_measures_train_df)
heart_measured_test = dataiku.Dataset("heart_measures_test")
heart_measured_test.write_with_schema(heart_measures_test_df)

• Run the recipe

Great! We can now go on the Flow, we’ll see an orange circle that represents your first step (we call it a Recipe) and two output datasets.

The Flow should now look like that: