Multi-Layer Plot

Combining multiple geometric layers in one visualization

Multi-layer plots combine different geometric elements (geoms) to create richer visualizations. Each DRAW clause adds a new layer.

Code

SELECT Date, Temp FROM ggsql:airquality
VISUALISE Date AS x, Temp AS y
DRAW line
    SETTING color => 'steelblue'
DRAW point
    SETTING size => 4, color => 'darkblue'
SCALE x VIA date
LABEL
    title => 'Temperature with Line and Points',
    x => 'Date',
    y => 'Temperature (F)'

Explanation

• The first DRAW line creates a line connecting all points
• The second DRAW point adds point markers at each data point
• SETTING on each layer controls that layer’s visual properties
• Both layers share the same x and y mappings from VISUALISE

Variations

Different Aesthetics Per Layer

Each layer can have its own aesthetic mappings using MAPPING:

SELECT Date, Temp, Ozone FROM ggsql:airquality
VISUALISE Date AS x
DRAW line
    MAPPING Temp AS y, 'Temperature' AS color
DRAW line
    MAPPING Ozone AS y, 'Ozone' AS color
SCALE x VIA date
LABEL
    title => 'Temperature and Ozone Over Time',
    x => 'Date',
    y => 'Value'

Layers from Different Data Sources

Use MAPPING ... FROM to pull each layer from different CTEs:

WITH temps AS (
    SELECT Date, Temp as value FROM ggsql:airquality
),
ozone AS (
    SELECT Date, Ozone as value FROM ggsql:airquality WHERE Ozone IS NOT NULL
)
VISUALISE
DRAW line
    MAPPING Date AS x, value AS y, 'Temperature' AS color FROM temps
DRAW point
    MAPPING Date AS x, value AS y, 'Ozone' AS color FROM ozone
    SETTING size => 3
SCALE x VIA date
LABEL
    title => 'Temperature vs Ozone',
    x => 'Date',
    y => 'Value'