Using Style feature to symbolize layers in QGIS

 Here, we will be using the Style feature in the Layer Properties box in QGIS. It is similar to the same system of applying symbology in ArcMap 10.2.

Task

- We will style the map qualitatively (Categorized based on color) by using unique colors to categorize the different states into regions.

- We will use Style feature (Graduated colors) to quantify and compare the population sizes by grouping the States into Low, Medium and High population based on a Color gradient.

- We will Style the map using Rule based color symbols to delineate the States with more females or more males.

Procedure

Qualitatively by using unique colors to categorize the different States into their regions

Shapefile of Administrative map of Nigeria showing all the States and their boundaries. Right Click and Go to Properties.


Let us take a look at the Attribute table first and see the 2006 Census data of the States.


In the Layer Properties dialog box, Go to Style. The Single Symbol (red box) is the default symbol for the layer.



Click on the drop down list and choose Categorized. Select the Column containing the ‘Region’ and Click ‘Classify’ and each region will be allocated a unique color.


Quantify the population sizes and group the States into Low, Medium and High population based on a Color gradient

For this option, we want to display quantitative attributes by comparing the population sizes of the States on a gradient. The column census_Tot contains these data. On the drop down list  on the Layers Properties window, Choose Graduated. Choose Column – census_Tot and select a colour ramp, then click Classify. The classes we have chosen is 3 and we edited the legend to Low, Medium and High.Click Ok to apply the changes.



Rule based symbol where we delineate the States with more females or more males
Using Rule based style will allow the User set the rules for the symbols . In our demonstration, we put column filters or query expressions that set symbols for States with more females than males and States with more males than females. Here select Rule-based instead of General. We made use of the columns census_Fem and census_Mal.


The map shows a color symbol for States where there are more males and another color symbol for where are more females


we hope you enjoyed the demonstration.