When you create a categorical data from a continuous value data(e.g. categorical raster based on a slope, elevation etc.) or managing a category, reclassify function is key. This process is very important to create a potential map(suitable map, probability map, etc.).
Input raster
In this tutorial, we are going to use the below slope map. The map is colored by slope categories(e.g. 15 < slope <= 30). Its value is continuous(0-90 degree).
Reclassify the slope map
There are some functions to reclassify a raster in processing toolbox(including SAGA and GRASS). In this tutorial, we are going to Reclassify by table under Raster analysis. I am used to using the same function in ArcGIS. I thought that Reclassify by table in QGIS is simple and good to use.
Open Reclassify by table.
Go to Processing toolbox > Raster analysis > Reclassify by table > Change settings like below > Run
Check the result
Change the color settings to unique color using the new value. The original slope(continuous value) map has been converted to a categorical slope map!!
Farther analysis
You can use the map as one of factors of modeling. The simplest modeling is score based modeling using “weighted sum” concept.
Go with the flow 