Data manipulation and analysis

Importing Data in Java

Anthony Markham

VP Quant Developer

Column selection

.selectColumns() creates a new Table object

// Select specific columns by name
Table nameAndSalary = employees.selectColumns("Name", "Salary");

// Select by column type
Table numericColumns = employees.selectColumns(
    column -> column.type().equals(ColumnType.DOUBLE) ||
    column.type().equals(ColumnType.INTEGER));

Filtering data

Filter rows with .where()
Returns a new Table object

// Filter with a single condition
Table seniors = employees.where(
    employees.intColumn("Age").isGreaterThanOrEqualTo(65));

// Filtering using multiple conditions
Table targetGroup = employees.where(
    employees.intColumn("Age").isBetweenInclusive(30, 50)
        .and(employees.doubleColumn("Salary")
            .isGreaterThan(75000)));

Sorting data

Organize data with .sortOn()
- Sorts in ascending order
Returns a new sorted table
.sortDescending() for descending order

// Sort by a single column (ascending)
Table sortedBySalary = employees.sortOn("Salary");

// Sort by multiple columns (custom direction)
Table complexSort = employees
    .sortOn("Department") 
    .sortDescendingOn("Salary");

Aggregation with summarize

Compute summary statistics with .summarize()
Returns a new table

import tech.tablesaw.aggregate.AggregateFunctions.*;

// Summarize salary
Table deptSummary = employees.summarize("Salary", mean, count, max).apply();

Mean [Salary]	Count [Salary]	Max [Salary]
113606.20299999935	1000	199793

Applies to all numeric columns by default

Aggregation with summarize

More complex aggregations are possible

// Multiple aggregations
Table complexSummary = employees.summarize(
    "Salary", "Age", 
    mean, median, min, max).apply();

Mean [Salary]	Median [Salary]	Min [Salary]	Max [Salary]	Mean [Age]	Median [Age]	Min [Age]	Max [Age]
113606.2029	112667	30301	199793	45.6699	46	22	70

Core manipulation methods

.select() - Choose specific columns

Table selected = employees.select("Name", "Salary");

.where() - Filter rows based on conditions

Table filtered = employees.where(condition);

.sortOn() - Order data by columns

Table sorted = employees.sortOn("Department", "Salary");

.summarize() - Compute statistics

Table summary = employees.summarize("Salary", mean, max).apply();

Let's practice!

Importing Data in Java