I did a supervised classification of a Landsat image subset using my training data polygons. I used SAGA GIS for that and everything worked out fine. Now I am stuck since I have no clue how to prepare the confusion matrix using my test polygons!
I know that I need for each polygon the number of pixels of the different classes, i.e. a cross tabulation.
How could one achieve that?
And yes, I know that there is this semi-automatic image classification plugin for QGIS and so forth, but I would like to understand the process of generating the confusion matrix itself from scratch.