I have a polygon layer representing traffic cells (from VISUM) and I have a matrix in Excel format which contains the calculated amount of trips between each cell in the polygon layer. Now I want to calculate how many trips are done between cells that are lying within a given buffer. How would I have to set up the polygon layer with the traffic cells to be able to just calculate the cells within the buffer area?
I could join the polygon layer column containing the traffic cell ID with the Excel columns containing the same ID but after selecting the Cells within the buffer I would sum the trips between the cells within the buffer with all other cells - because the "target cells" would be rows after joining both layers. I can't get my head around a method that is allowing me to select the cells in a buffer area and limiting the calculation to sum up the trips just to the same cell. I am working with QGIS 3.4.2.