Titanic: tutorial and examples

imports

In [1]:
import dalex as dx

import pandas as pd
import numpy as np

from sklearn.neural_network import MLPClassifier
from sklearn.preprocessing import StandardScaler, OneHotEncoder
from sklearn.impute import SimpleImputer
from sklearn.pipeline import Pipeline
from sklearn.compose import ColumnTransformer

import warnings
warnings.filterwarnings('ignore')
In [2]:
dx.__version__
Out[2]:
'1.0.0'

load data

First, divide the data into variables X and a target variable y.

In [3]:
data = dx.datasets.load_titanic()

X = data.drop(columns='survived')
y = data.survived
In [4]:
data.head(10)
Out[4]:
gender age class embarked fare sibsp parch survived
0 male 42.0 3rd Southampton 7.1100 0 0 0
1 male 13.0 3rd Southampton 20.0500 0 2 0
2 male 16.0 3rd Southampton 20.0500 1 1 0
3 female 39.0 3rd Southampton 20.0500 1 1 1
4 female 16.0 3rd Southampton 7.1300 0 0 1
5 male 25.0 3rd Southampton 7.1300 0 0 1
6 male 30.0 2nd Cherbourg 24.0000 1 0 0
7 female 28.0 2nd Cherbourg 24.0000 1 0 1
8 male 27.0 3rd Cherbourg 18.1509 0 0 1
9 male 20.0 3rd Southampton 7.1806 0 0 1

create a pipeline model

  • numerical_transformer pipeline:

    • numerical_features: choose numerical features to transform
    • impute missing data with median strategy
    • scale numerical features with standard scaler

  • categorical_transformer pipeline:

    • categorical_features: choose categorical features to transform
    • impute missing data with 'missing' string
    • encode categorical features with one-hot

  • aggregate those two pipelines into a preprocessor using ColumnTransformer

  • make a basic classifier model using MLPClassifier - it has 3 hidden layers with sizes 150, 100, 50 respectively
  • construct a clf pipeline model, which combines the preprocessor with the basic classifier model
In [5]:
numerical_features = ['age', 'fare', 'sibsp', 'parch']
numerical_transformer = Pipeline(
    steps=[
        ('imputer', SimpleImputer(strategy='median')),
        ('scaler', StandardScaler())
    ]
)

categorical_features = ['gender', 'class', 'embarked']
categorical_transformer = Pipeline(
    steps=[
        ('imputer', SimpleImputer(strategy='constant', fill_value='missing')),
        ('onehot', OneHotEncoder(handle_unknown='ignore'))
    ]
)

preprocessor = ColumnTransformer(
    transformers=[
        ('num', numerical_transformer, numerical_features),
        ('cat', categorical_transformer, categorical_features)
    ]
)

classifier = MLPClassifier(hidden_layer_sizes=(150,100,50), max_iter=500, random_state=0)

clf = Pipeline(steps=[('preprocessor', preprocessor),
                      ('classifier', classifier)])

fit the model

In [6]:
clf.fit(X, y)
Out[6]:
Pipeline(steps=[('preprocessor',
                 ColumnTransformer(transformers=[('num',
                                                  Pipeline(steps=[('imputer',
                                                                   SimpleImputer(strategy='median')),
                                                                  ('scaler',
                                                                   StandardScaler())]),
                                                  ['age', 'fare', 'sibsp',
                                                   'parch']),
                                                 ('cat',
                                                  Pipeline(steps=[('imputer',
                                                                   SimpleImputer(fill_value='missing',
                                                                                 strategy='constant')),
                                                                  ('onehot',
                                                                   OneHotEncoder(handle_unknown='ignore'))]),
                                                  ['gender', 'class',
                                                   'embarked'])])),
                ('classifier',
                 MLPClassifier(hidden_layer_sizes=(150, 100, 50), max_iter=500,
                               random_state=0))])

create an explainer for the model

In [7]:
exp = dx.Explainer(clf, X, y)

Preparation of a new explainer is initiated

  -> data              : 2207 rows 7 cols
  -> target variable   : Parameter 'y' was a pandas.Series. Converted to a numpy.ndarray.
  -> target variable   : 2207 values
  -> model_class       : sklearn.neural_network._multilayer_perceptron.MLPClassifier (default)
  -> label             : Not specified, model's class short name will be used. (default)
  -> predict function  : <function yhat_proba_default at 0x00000286FFF84820> will be used (default)
  -> predict function  : Accepts only pandas.DataFrame, numpy.ndarray causes problems.
  -> predicted values  : min = 2.72e-06, mean = 0.337, max = 1.0
  -> model type        : classification will be used (default)
  -> residual function : difference between y and yhat (default)
  -> residuals         : min = -0.921, mean = -0.0146, max = 0.975
  -> model_info        : package sklearn

A new explainer has been created!

introduction to the topic: Explanatory Model Analysis: Explore, Explain, and Examine Predictive Models

Above functionalities are accessible from the Explainer object through its methods.

Model-level and predict-level methods return a new unique object that contains the result attribute (pandas.DataFrame) and the plot method.

Predict-level explanations

predict

This function is nothing but normal model prediction, however it uses Explainer interface.

Let's create two example persons for this tutorial.

In [8]:
john = pd.DataFrame({'gender': ['male'],
                       'age': [25],
                       'class': ['1st'],
                       'embarked': ['Southampton'],
                       'fare': [72],
                       'sibsp': [0],
                       'parch': 0},
                      index = ['John'])
In [9]:
mary = pd.DataFrame({'gender': ['female'],
                     'age': [35],
                     'class': ['3rd'],
                     'embarked': ['Cherbourg'],
                     'fare': [25],
                     'sibsp': [0],
                     'parch': [0]},
                     index = ['Mary'])

You can make a prediction on many samples at the same time

In [10]:
exp.predict(X)[0:10]
Out[10]:
array([0.07907226, 0.20628711, 0.13463174, 0.60372994, 0.76485216,
       0.16150944, 0.03705073, 0.99324938, 0.19563509, 0.12184964])

As well as on only one instance. However, the only accepted format is pandas.DataFrame.

Prediction of survival for John.

In [11]:
exp.predict(john)
Out[11]:
array([0.08127727])

Prediction of survival for Mary.

In [12]:
exp.predict(mary)
Out[12]:
array([0.8929144])

predict_parts

  • 'break_down'

  • 'break_down_interactions'

  • 'shap'

This function calculates Variable Attributions as Break Down, iBreakDown or Shapley Values explanations.

Model prediction is decomposed into parts that are attributed for particular variables.

In [13]:
bd_john = exp.predict_parts(john, type='break_down', label=john.index[0])
bd_interactions_john = exp.predict_parts(john, type='break_down_interactions', label="John+")

sh_mary = exp.predict_parts(mary, type='shap', B = 10, label=mary.index[0])
In [14]:
bd_john.result
Out[14]:
variable_name variable_value variable cumulative contribution sign position label
0 intercept 1 intercept 0.336735 0.336735 1.0 8 John
1 class 1st class = 1st 0.583093 0.246358 1.0 7 John
2 age 25.0 age = 25.0 0.595401 0.012308 1.0 6 John
3 sibsp 0.0 sibsp = 0.0 0.585751 -0.009650 -1.0 5 John
4 fare 72.0 fare = 72.0 0.319029 -0.266722 -1.0 4 John
5 parch 0.0 parch = 0.0 0.300772 -0.018257 -1.0 3 John
6 embarked Southampton embarked = Southampton 0.284191 -0.016580 -1.0 2 John
7 gender male gender = male 0.081277 -0.202914 -1.0 1 John
8 prediction 0.081277 0.081277 1.0 0 John
In [15]:
bd_john.plot(bd_interactions_john)