Perform classification with a boosted tree model

This tutorial teaches you how to use a boosted tree classifier model to predict the income range of individuals based on their demographic data. The model predicts whether a value falls into one of two categories, in this case whether an individual's annual income falls above or below $50,000.

This tutorial uses the bigquery-public-data.ml_datasets.census_adult_income dataset. This dataset contains the demographic and income information of US residents from 2000 and 2010.

Objectives

This tutorial guides you through completing the following tasks:

Creating a boosted tree model to predict census respondents' income bracket by using the CREATE MODEL statement.
Evaluating the model by using the ML.EVALUATE function.
Getting predictions from the model by using the ML.PREDICT function.

Costs

This tutorial uses billable components of Google Cloud, including the following:

BigQuery
BigQuery ML

For more information about BigQuery costs, see the BigQuery pricing page.

For more information about BigQuery ML costs, see BigQuery ML pricing.

Before you begin

Sign in to your Google Cloud account. If you're new to Google Cloud, create an account to evaluate how our products perform in real-world scenarios. New customers also get $300 in free credits to run, test, and deploy workloads.

In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

Go to project selector

Make sure that billing is enabled for your Google Cloud project.

In the Google Cloud console, on the project selector page, select or create a Google Cloud project.

Go to project selector

Make sure that billing is enabled for your Google Cloud project.

BigQuery is automatically enabled in new projects. To activate BigQuery in a pre-existing project, go to
Enable the BigQuery API.
Enable the API

Required Permissions

To create the dataset, you need the bigquery.datasets.create IAM permission.
To create the connection resource, you need the following permissions:
- bigquery.connections.create
- bigquery.connections.get
To create the model, you need the following permissions:
- bigquery.jobs.create
- bigquery.models.create
- bigquery.models.getData
- bigquery.models.updateData
- bigquery.connections.delegate
To run inference, you need the following permissions:
- bigquery.models.getData
- bigquery.jobs.create

For more information about IAM roles and permissions in BigQuery, see Introduction to IAM.

Create a dataset

Create a BigQuery dataset to store your ML model:

In the Google Cloud console, go to the BigQuery page.

Go to the BigQuery page
In the Explorer pane, click your project name.
Click View actions > Create dataset.
On the Create dataset page, do the following:
- For Dataset ID, enter bqml_tutorial.
- For Location type, select Multi-region, and then select US (multiple regions in United States).
  
  The public datasets are stored in the US multi-region. For simplicity, store your dataset in the same location.
- Leave the remaining default settings as they are, and click Create dataset.

Prepare the sample data

The model you create in this tutorial predicts the income bracket for census respondents, based on the following features:

Age
Type of work performed
Marital status
Level of education
Occupation
Hours worked per week

The education column isn't included in the training data, because the education and education_num columns both express the respondent's level of education in different formats.

You separate the data into training, evaluation, and prediction sets by creating a new dataframe column that is derived from the functional_weight column. Eighty percent of the data is used for training the model, and the remaining twenty percent of the data is used for evaluation and prediction.

SQL

To prepare your sample data, create a view to contain the training data. This view is used by the CREATE MODEL statement later in this tutorial.

Run the query that prepares the sample data:

In the Google Cloud console, go to the BigQuery page.

Go to BigQuery

In the query editor, run the following query:

CREATE OR REPLACE VIEW
  `bqml_tutorial.input_data` AS
SELECT
  age,
  workclass,
  marital_status,
  education_num,
  occupation,
  hours_per_week,
  income_bracket,
  CASE
    WHEN MOD(functional_weight, 10) < 8 THEN 'training'
    WHEN MOD(functional_weight, 10) = 8 THEN 'evaluation'
    WHEN MOD(functional_weight, 10) = 9 THEN 'prediction'
  END AS dataframe
FROM
  `bigquery-public-data.ml_datasets.census_adult_income`;

In the Explorer pane, expand the bqml_tutorial dataset and locate the input_data view.
Click the view name to open the information pane. The view schema appears in the Schema tab.

BigQuery DataFrames

Create a DataFrame called input_data. You use input_data later in this tutorial to use to train the model, evaluate it, and make predictions.

Before trying this sample, follow the BigQuery DataFrames setup instructions in the BigQuery quickstart using BigQuery DataFrames. For more information, see the BigQuery DataFrames reference documentation.

To authenticate to BigQuery, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import bigframes.pandas as bpd

input_data = bpd.read_gbq(
    "bigquery-public-data.ml_datasets.census_adult_income",
    columns=(
        "age",
        "workclass",
        "marital_status",
        "education_num",
        "occupation",
        "hours_per_week",
        "income_bracket",
        "functional_weight",
    ),
)
input_data["dataframe"] = bpd.Series("training", index=input_data.index,).case_when(
    [
        (((input_data["functional_weight"] % 10) == 8), "evaluation"),
        (((input_data["functional_weight"] % 10) == 9), "prediction"),
    ]
)
del input_data["functional_weight"]

Create the boosted tree model

Create a boosted tree model to predict census respondents' income bracket, and train it on the census data. The query takes about 30 minutes to complete.

SQL

Follow these steps to create the model:

In the Google Cloud console, go to the BigQuery page.

Go to BigQuery

In the query editor, paste in the following query and click Run:

CREATE MODEL `bqml_tutorial.tree_model`
OPTIONS(MODEL_TYPE='BOOSTED_TREE_CLASSIFIER',
        BOOSTER_TYPE = 'GBTREE',
        NUM_PARALLEL_TREE = 1,
        MAX_ITERATIONS = 50,
        TREE_METHOD = 'HIST',
        EARLY_STOP = FALSE,
        SUBSAMPLE = 0.85,
        INPUT_LABEL_COLS = ['income_bracket'])
AS SELECT * EXCEPT(dataframe)
FROM `bqml_tutorial.input_data`
WHERE dataframe = 'training';

After the query completes, the tree_model model appears in the Explorer pane. Because the query uses a CREATE MODEL statement to create a model, you don't see query results.

BigQuery DataFrames

To authenticate to BigQuery, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

from bigframes.ml import ensemble

# input_data is defined in an earlier step.
training_data = input_data[input_data["dataframe"] == "training"]
X = training_data.drop(columns=["income_bracket", "dataframe"])
y = training_data["income_bracket"]

# create and train the model
tree_model = ensemble.XGBClassifier(
    n_estimators=1,
    booster="gbtree",
    tree_method="hist",
    max_iterations=1,  # For a more accurate model, try 50 iterations.
    subsample=0.85,
)
tree_model.fit(X, y)

tree_model.to_gbq(
    your_model_id,  # For example: "your-project.bqml_tutorial.tree_model"
    replace=True,
)

Evaluate the model

SQL

Follow these steps to evaluate the model:

In the Google Cloud console, go to the BigQuery page.

Go to BigQuery

In the query editor, paste in the following query and click Run:

  SELECT
    *
  FROM
    ML.EVALUATE (MODEL `bqml_tutorial.tree_model`,
      (
      SELECT
        *
      FROM
        `bqml_tutorial.input_data`
      WHERE
        dataframe = 'evaluation'
      )
    );

The results should look similar to the following:

+---------------------+---------------------+---------------------+-------------------+---------------------+---------------------+
| precision           | recall              | accuracy            | f1_score          | log_loss            | roc_auc             |
+---------------------+---------------------+---------------------+-------------------+-------------------------------------------+
| 0.67192429022082023 | 0.57880434782608692 | 0.83942963422194672 | 0.621897810218978 | 0.34405456040833338 | 0.88733566433566435 |
+---------------------+---------------------+ --------------------+-------------------+---------------------+---------------------+

BigQuery DataFrames

To authenticate to BigQuery, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

# Select model you'll use for predictions. `read_gbq_model` loads model
# data from BigQuery, but you could also use the `tree_model` object
# from the previous step.
tree_model = bpd.read_gbq_model(
    your_model_id,  # For example: "your-project.bqml_tutorial.tree_model"
)

# input_data is defined in an earlier step.
evaluation_data = input_data[input_data["dataframe"] == "evaluation"]
X = evaluation_data.drop(columns=["income_bracket", "dataframe"])
y = evaluation_data["income_bracket"]

# The score() method evaluates how the model performs compared to the
# actual data. Output DataFrame matches that of ML.EVALUATE().
score = tree_model.score(X, y)
score.peek()
# Output:
#    precision    recall  accuracy  f1_score  log_loss   roc_auc
# 0   0.671924  0.578804  0.839429  0.621897  0.344054  0.887335

The evaluation metrics indicate good model performance, in particular, the fact that the roc_auc score is greater than 0.8.

For more information about the evaluation metrics, see Classification models.

Use the model to predict classifications

SQL

Follow these steps to forecast data with the model:

In the Google Cloud console, go to the BigQuery page.

Go to BigQuery

In the query editor, paste in the following query and click Run:

  SELECT
    *
  FROM
    ML.PREDICT (MODEL `bqml_tutorial.tree_model`,
      (
      SELECT
        *
      FROM
        `bqml_tutorial.input_data`
      WHERE
        dataframe = 'prediction'
      )
    );

The first few columns of the results should look similar to the following:

  +---------------------------+--------------------------------------+-------------------------------------+
  | predicted_income_bracket  | predicted_income_bracket_probs.label | predicted_income_bracket_probs.prob |
  +---------------------------+--------------------------------------+-------------------------------------+
  |  <=50K                    |  >50K                                | 0.05183430016040802                 |
  +---------------------------+--------------------------------------+-------------------------------------+
  |                           |  <50K                                | 0.94816571474075317                 |
  +---------------------------+--------------------------------------+-------------------------------------+
  |  <=50K                    |  >50K                                | 0.00365859130397439                 |
  +---------------------------+--------------------------------------+-------------------------------------+
  |                           |  <50K                                | 0.99634140729904175                 |
  +---------------------------+--------------------------------------+-------------------------------------+
  |  <=50K                    |  >50K                                | 0.037775970995426178                |
  +---------------------------+--------------------------------------+-------------------------------------+
  |                           |  <50K                                | 0.96222406625747681                 |
  +---------------------------+--------------------------------------+-------------------------------------+

BigQuery DataFrames

To authenticate to BigQuery, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

# Select model you'll use for predictions. `read_gbq_model` loads model
# data from BigQuery, but you could also use the `tree_model` object
# from previous steps.
tree_model = bpd.read_gbq_model(
    your_model_id,  # For example: "your-project.bqml_tutorial.tree_model"
)

# input_data is defined in an earlier step.
prediction_data = input_data[input_data["dataframe"] == "prediction"]

predictions = tree_model.predict(prediction_data)
predictions.peek()
# Output:
# predicted_income_bracket   predicted_income_bracket_probs.label  predicted_income_bracket_probs.prob
#                   <=50K                                   >50K                   0.05183430016040802
#                                                           <50K                   0.94816571474075317
#                   <=50K                                   >50K                   0.00365859130397439
#                                                           <50K                   0.99634140729904175
#                   <=50K                                   >50K                   0.037775970995426178
#                                                           <50K                   0.96222406625747681

The predicted_income_bracket contains the predicted value from the model. The predicted_income_bracket_probs.label shows the two labels that the model had to choose between, and the predicted_income_bracket_probs.prob column shows the probability of the given label being the correct one.

For more information about the output columns, see Classification models.

Clean up

To avoid incurring charges to your Google Cloud account for the resources used in this tutorial, either delete the project that contains the resources, or keep the project and delete the individual resources.

You can delete the project you created.
Or you can keep the project and delete the dataset.

Delete your dataset

Deleting your project removes all datasets and all tables in the project. If you prefer to reuse the project, you can delete the dataset you created in this tutorial:

If necessary, open the BigQuery page in the Google Cloud console.

Go to the BigQuery page
In the navigation, click the bqml_tutorial dataset you created.
Click Delete dataset on the right side of the window. This action deletes the dataset, the table, and all the data.
In the Delete dataset dialog, confirm the delete command by typing the name of your dataset (bqml_tutorial) and then click Delete.

Delete your project

To delete the project:

In the Google Cloud console, go to the Manage resources page.
Go to Manage resources
In the project list, select the project that you want to delete, and then click Delete.
In the dialog, type the project ID, and then click Shut down to delete the project.

What's next

Learn how to create a logistic regression classification model.
For an overview of BigQuery ML, see Introduction to AI and ML in BigQuery.