Solving a Classification Problem Using the Decision Tree Algorithm With Oracle
Learn how to solve a classification problem in Oracle by looking at an example that uses an interesting HR analytics dataset.
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In this article, I will solve a classification problem with Oracle data mining.
Data science and machine learning are very popular today. But these subjects require extensive knowledge and application expertise. We can solve these problems with various products and software that have been developed by various companies. In Oracle, methods and algorithms for solving these problems are presented to users with the
DBMS_DATA_MINING package, we can create models such as clustering, classification, regression, anomaly detection, feature extraction, and association. We can interpret efficiency with the models we create. The results we obtain from these models can be put into our business scenario.
DBMS_DATA_MINING package does not come up by default on the Oracle database. For this reason, it's necessary to install this package first. You can set up your database Oracle Data Mining by following this link.
With the installation of the Oracle Data Mining package, three new dictionary tables are created:
SELECT * FROM ALL_MINING_MODELS;
SELECT * FROM ALL_MINING_MODEL_SETTINGS;
SELECT * FROM ALL_MINING_MODEL_ATTRIBUTES;
ALL_MINING_MODELS table contains information about all the models.
ALL_MINING_MODELS_ATTRIBUTES tables contain parameters and specific details about these models.
Now, let's prepare an easily understood data set to solve a sample classification problem.
Let's first examine the
HR_ANALYTICS data set consists of ten (eight numeric, two string) columns and contains 15,000 records. The description of each column in the
HR_ANALYTICS dataset is given below.
|Column Name||Description||Data Type|
||Level of satisfaction (0-1)||Numeric|
||Time since last performance evaluation (in years)||Numeric|
||Number of projects completed while at work||Numeric|
||Average monthly hours at workplace||Numeric|
||Number of years spent in the company||Numeric|
||Whether the employee had a workplace accident||Numeric|
||Whether the employee left the workplace (1 or 0 factor)||Numeric|
||Whether the employee was promoted in the last five years||Numeric|
||Department in which they work||String|
||Relative level of salary (high)||
Now that we have reviewed the details with our dataset, let's load the
HR_ANALYTICS that we downloaded to our Oracle database.
First, create the Oracle table in which we will load the data set (CSV) that we downloaded.
CREATE TABLE hr_data ( satisfaction_level NUMBER, last_evaluation NUMBER, number_project NUMBER, average_montly_hours NUMBER, time_spend_company NUMBER, Work_accident NUMBER, left NUMBER, promotion_last_5years NUMBER, sales VARCHAR2 (20), salary VARCHAR2 (20) );
Now that we have created our table, we will load the dataset we downloaded as CSV into the table; we have multiple methods to do this:
Using Oracle External Table
Using Oracle SQL Loader
Using SQL-PL/SQL editors (Oracle SQL Developer, Toad, PL/SQL Developer...)
I will load the dataset with the editor that I am using. I use Toad as an editor. With Toad, you can perform the data loading process by following the steps below.
Database > Import > Import Table Data
You may not be using this editor because Toad is paid. This feature is available to other editors, so you can easily do this with other editors. For example, with Oracle SQL Developer for free, you can load data as follows using Oracle SQL Developer.
SELECT * FROM HR_DATA;
We have completed the dataset installation process. Now let's determine which columns we will use for classification.
When we examine our data set, we see that there is some information about each employee. At the end of this information, the employee's salary (
SALARY) was given (low-medium-high). We will produce our model using a large part of the data set (training set). We will then test the model using the rest of the data (test set). Finally, we will compare the actual results with the results produced by the model we build.
First, let's separate our data set into two separate clusters: training (70%) and test (30%).
CREATE TABLE HR_DATA_MAIN AS SELECT * FROM (SELECT ROWNUM RN, SATISFACTION_LEVEL, LAST_EVALUATION, NUMBER_PROJECT, AVERAGE_MONTLY_HOURS, TIME_SPEND_COMPANY, WORK_ACCIDENT, LEFT, PROMOTION_LAST_5YEARS, SALES, SALARY FROM HR_DATA); CREATE TABLE HR_DATA_TRAINING AS SELECT SATISFACTION_LEVEL, LAST_EVALUATION, NUMBER_PROJECT, AVERAGE_MONTLY_HOURS, TIME_SPEND_COMPANY, WORK_ACCIDENT, LEFT, PROMOTION_LAST_5YEARS, SALES, SALARY FROM HR_DATA_MAIN WHERE RN < 10500; CREATE TABLE HR_DATA_TEST AS SELECT SATISFACTION_LEVEL, LAST_EVALUATION, NUMBER_PROJECT, AVERAGE_MONTLY_HOURS, TIME_SPEND_COMPANY, WORK_ACCIDENT, LEFT, PROMOTION_LAST_5YEARS, SALES, SALARY FROM HR_DATA_MAIN WHERE RN >= 10500;
We prepared our training and test data set. Now let's create our table that we will read the algorithm settings and enter the algorithm parameters we will use in this table. We do not have to enter all the parameters necessary for the operation of the algorithm. If we do not define the optional parameters, Oracle uses these parameters with default values in the system. You can find the parameters defined for the decision tree algorithm and the default values for these parameters below.
CREATE TABLE DTSETTINGS ( SETTING_NAME VARCHAR2 (200), SETTING_VALUE VARCHAR2 (200) ); BEGIN INSERT INTO DTSETTINGS VALUES ('ALGO_NAME', 'ALGO_DECISION_TREE'); INSERT INTO DTSETTINGS VALUES (dbms_data_mining.tree_impurity_metric, 'TREE_IMPURITY_ENTROPY'); COMMIT; END;
We separated our data set as training and testing, and then we created our algorithm settings. Now, we can move on to the step of creating our model.
BEGIN DBMS_DATA_MINING.CREATE_MODEL ( model_name => 'DT_MODEL', mining_function => DBMS_DATA_MINING.CLASSIFICATION, data_table_name => 'HR_DATA_TRAINING', case_id_column_name => NULL, target_column_name => 'SALARY', settings_table_name => 'DTSETTINGS'); END;
Now that we have our model, let's look at the details about the model now from the dictionary.
SELECT MODEL_NAME, ALGORITHM, COMMENTS, CREATION_DATE, MINING_FUNCTION, MODEL_SIZE FROM ALL_MINING_MODELS WHERE MODEL_NAME = 'DT_MODEL';
SELECT SETTING_NAME, SETTING_VALUE FROM ALL_MINING_MODEL_SETTINGS WHERE MODEL_NAME = 'DT_MODEL';
Now that we have seen the details about our model, we can now use our model to make predictions through our test data set.
SELECT T.SALARY ACTUAL, PREDICTION (DT_MODEL USING *) MODEL_PREDICT_RESPONSE, PREDICTION_PROBABILITY (DT_MODEL USING *) MODEL_PROBABILTY_RESPONSE FROM HR_DATA_TEST T;
We applied our model to our test data set and observed the estimates that our model produced.
We can calculate the performance of the model we build by ourselves, as well as use the
DBMS_DATA_MINING.COMPUTE_CONFUSION_MATRIX ( accuracy OUT NUMBER, apply_result_table_name IN VARCHAR2, target_table_name IN VARCHAR2, case_id_column_name IN VARCHAR2, target_column_name IN VARCHAR2, confusion_matrix_table_name IN VARCHAR2, score_column_name IN VARCHAR2 DEFAULT 'PREDICTION', score_criterion_column_name IN VARCHAR2 DEFAULT 'PROBABILITY', cost_matrix_table_name IN VARCHAR2 DEFAULT NULL, apply_result_schema_name IN VARCHAR2 DEFAULT NULL, target_schema_name IN VARCHAR2 DEFAULT NULL, cost_matrix_schema_name IN VARCHAR2 DEFAULT NULL, score_criterion_type IN VARCHAR2 DEFAULT 'PROBABILITY');
Detailed explanations of the use of
DBMS_DATA_MINING.COMPUTE_CONFUSION_MATRIX method can be found here.
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