Representing five categories of data in one symbol using QGIS

Question

I have been given the big task of representing a lot of data in one symbol. The plan is to represent 5 categories of data in one symbol.

I hope to do this by changing factors such as:

• Fill colour
• Border colour
• Shape
• Orientation
• Size

I planned on having:

• Severity - changing border colour:
  - Serious - red
  - Slight - yellow
• Road surface conditions - changing shape:
  - Dry - triangle
  - Wet - square
• Light conditions - changing size:
  - Dark - small (4 points for example)
  - Light - large (8 points maybe)
• Weather conditions - changing orientation:
  - Fine - vertical
  - Raining - 45 degrees clockwise
• Casualty mode of transport - changing fill colour:
  - Pedal cycle - purple
  - Pedestrian - green
  - Moped - cyan
  - Car - black
  - Bus - white

Is there any way of doing this without typing out 80 separate statements and changing each variable individually?

Answer 1

Using "Data defined override > Edit...", use the following expressions. (Edit field names)

For "Size":

CASE
  WHEN "Light"='Dark' THEN 4
  WHEN "Light"='Light' THEN 8
END

For "Fill color":

CASE
  WHEN "Casualty mode"='Pedal cycle' THEN 'purple'
  WHEN "Casualty mode"='Pedestrian' THEN 'green'
  WHEN "Casualty mode"='Moped' THEN 'cyan'
  WHEN "Casualty mode"='Car' THEN 'black'
  WHEN "Casualty mode"='Bus' THEN 'white'
END

For "Stroke color":

CASE
  WHEN "Severity"='Serious' THEN 'red'
  WHEN "Severity"='Slight' THEN 'yellow'
END

For "Rotation":

CASE
  WHEN "Weather"='Fine' THEN 0
  WHEN "Weather"='Raining' THEN 45
END

For "Shape":

CASE
  WHEN "Road surface"='Dry' THEN 'triangle'
  WHEN "Road surface"='Wet' THEN 'square'
END

Toy data and result:

Answer 2

All of your visual variables can be driven by expressions so you need to write 5 expressions with a number of cases for each variable.

For Example

case 
when  "conditions"  =  'wet' then 'square'
when  "conditions"  =  'dry' then 'triangle'
end