ZMedia Purwodadi

QGis Data Exploration Tutorial

Table of Contents

Exploring Data

This is Section 5 - Part of Qgis Comprehensive Tutorial

Exploring data is a fundamental part of working with QGIS. This section will cover how to view, query, and manipulate your data using QGIS tools and features effectively.

1. Opening the Attribute Table

The attribute table provides a detailed view of the data associated with your vector layers. Here's how to access and explore it:

Steps to Open the Attribute Table:

  1. Right-click on the layer in the Layers Panel.
  2. Select Open Attribute Table from the context menu.

The attribute table will open in a new window, displaying all attributes and allowing you to perform various actions.

Understanding the Attribute Table

In the attribute table, each row represents a feature, and each column represents an attribute. You can:

  • Sort: Click on the column header to sort by that attribute.
  • Filter: Use the filter option to display only records that meet specific criteria.
  • Edit: Toggle the editing mode to make changes to the attribute values.
Note: Always ensure to save your changes after editing attributes by clicking the Save Edits button.

2. Using the Identify Features Tool

The Identify Features tool allows you to click on a feature in the map canvas to view its attributes quickly.

How to Use the Identify Features Tool:

  1. Select the Identify Features tool from the toolbar (an icon that looks like a cursor with a question mark).
  2. Click on the feature you want to explore in the map canvas.
  3. A popup will appear, displaying the attributes of that feature.

3. Exploring Data with Filtering

Filtering allows you to focus on specific records in your attribute table. This can be done using the following methods:

3.1 Simple Filter

In the attribute table:

  1. Click the Show Selected Features button to filter only selected features.
  2. Use the filter expression dialog by clicking the Filter button.

3.2 Advanced Filtering

For more complex filtering, use the expression builder:

  1. Open the attribute table, and click on the Advanced Filter button.
  2. Construct your expression using fields and operators (e.g., "population" > 10000).
  3. Click OK to apply the filter.
Tip: Save your filtered view as a new layer by exporting it through the attribute table options.

4. Visualization and Symbology

Visual representation of data is essential for effective communication. QGIS allows you to customize the symbology of your layers:

4.1 Changing Layer Symbology

Steps to Change Symbology:

  1. Right-click on the layer in the Layers Panel and select Properties.
  2. Navigate to the Symbology tab.
  3. Select the style type (Single Symbol, Graduated, Categorized, etc.).
  4. Configure the options based on your data (e.g., colors, size).
  5. Click OK to apply changes.

4.2 Using Styles

You can save your customized styles for future use:

  1. In the Layer Properties dialog, navigate to the Style tab.
  2. Click Save Style to store your current symbology settings.
  3. Load saved styles in future projects to maintain consistency.
Note: Consider using color ramps for better visualization of quantitative data.

5. Common Questions

How can I view multiple layers at once?
You can add multiple layers to your project and adjust their visibility in the Layers Panel. Use transparency settings to see overlapping layers.
What should I do if the attribute table is empty?
Check if the layer is properly loaded and ensure that it has valid data. If it’s a new layer, make sure features have been created.
Can I perform calculations in the attribute table?
Yes! You can use the field calculator in the attribute table to create new fields or update existing ones with calculations based on other attributes.
Reminder: Regularly back up your QGIS project and data to prevent data loss during your work.
This section includes enhanced styling for better readability and user engagement. Feel free to adjust any elements or content! Let me know if you need further modifications or additions.