I have distribution data of a set of species (plants, mosses and lichens: 13 species total) in the Netherlands. I made a grid that divides the Netherlands into 1x1 km squares. I am not interested in how many points of a single species are within a square. I used the TomBio addon to transform the species point data into 1x1 km squares, so that they match the grid (i.e. ten points of a species in a gridcell are now one 1x1 km square. Also, one species in a gridcell is now a 1x1 km square).
I want to make an estimate of the distribution of the community these species occur in. Every species has a weighing value related to how much they are bound to the community i want to estimate the distribution of. This means that some species that do occur in the community, but also occur in other communities get a value of 1. Species that occur solely in this community get a value of 10. Of course this is different for each of the 13 species.
Based on the weighing values, i determined a threshold value. i.e, if the sum of weighing values (determined by the species that occur) within a grid cell exceed this threshold, i can assume that the community occurs in that gridcell.
To make the whole story a bit more comprehensible:
Species Weighing value A 2 B 4 C 6 D 6 E 10
If the sum of the values in a grid is say twelve or more, I assume the community is present there. See below for a heads example of the attribute tables.
How can I use QGIS to calcuate within a gridcell the value of the sum of the appointed weighing values, and if the threshold is exceeded, the gridcell gets a color?
I know how to count the individual blocks (species) in a gridcell, but I havn't worked out a way to include the weighing values in this process.