QGIS is a powerful Geographic Information System (GIS) software, renowned for its modularity thanks to its numerous plugins. Among these, Data Plotly stands out for its ability to create interactive graphics directly from GIS layers. A valuable tool for complementing spatial analysis with non-cartographic visual representations.
Why use Data Plotly?
When you’re working on a GIS project, it’s not uncommon to want to visually explore the relationships between different variables: number of dwellings per district, agricultural area per municipality, population variation, and so on.
Data Plotly fills this need by enabling you to create :
- histograms,
- bar or pie charts,
- scatter plots,
- boxplots,
- line graphs,
- correlation matrices,
- etc.
… all without leaving QGIS.
Plugin installation
- Open QGIS.
- Go to Extensions > Install/Manage Extensions.
- Search for Data Plotly, then click on Install.
- Once installed, you’ll find the tool in the Extensions > Data Plotly menu or via a graphic icon in the toolbar.
Create a graph in just a few clicks
Here’s a simple example for a layer containing statistical data by region:
- Select your vector layer (e.g.: communes, regions…).
- Launch Data Plotly.
- In the window that opens :
- Choose the chart type (e.g. Bar Plot).
- Specify the field for the X axis (e.g.: region names).
- Specify the field for the Y axis (e.g.: population, area, etc.).
- Click on Create Plot.
The plot is displayed in an interactive window. You can zoom in, hover over the data, and even save the plot as an image.
Advanced functions
- Dynamic selection: click on an element in the graph to see the corresponding selection on the map.
- Filters: you can work only with entities selected in QGIS.
- Multiple graphics: generate multiple types of graphics to compare variables.
- Customization: colors, titles, labels, axis orientation…
Real-life use cases
Here are a few examples of how you can use QGIS in real-life projects:
| Cases | Usage |
|---|---|
| Forest inventory | Sector diagram of tree species |
| Urbanism | Histogram of number of dwellings by type |
| Environmental monitoring | Line graph showing the evolution of an indicator over time |
| Agriculture | Boxplot of cultivated area by type of crop |
Export and integration
- You can save graphics (PNG, SVG…) for your reports.
- You can also copy the graph to the clipboard for insertion in a Word document or slide.
Limitations
- Data Plotly does not yet support the export of graphical data (e.g. values behind a boxplot).
- No automatic chart update if data changes (generation must be restarted).
- Interface sometimes limited for very large data sets.
Alternative: the basic graph integrated into QGIS?
QGIS also offers a basic graphing tool via View > Panels > Data Plot Panel, useful for bars and simple time series.
But Data Plotly is richer and more flexible, especially for exploratory statistical analysis.
In a nutshell
The Data Plotly plugin is an excellent addition for any QGIS user wishing to go beyond maps and integrate graphical analysis into their GIS workflow. Intuitive, interactive and powerful, it lets you cross statistical and spatial perspectives without leaving the QGIS environment. QGIS souhaitant aller au-delà des cartes et intégrer l’analyse graphique dans son flux de travail SIG. Intuitif, interactif, et puissant, il permet de croiser les regards statistiques et spatiaux sans quitter l’environnement QGIS.
Coming soon on the blog
In a future article, we’ll look at how to combine Data Plotly with interactive selections and filters to refine field data analysis.
