I've encountered the following problem frequently when I am using the raster calculator, even though sometimes the calculator works. However, I cannot figure out the difference between the times it works and the ones it does not.
The raster layer I am using is a gridded population. I want to create a mask layer with 1 meaning that there exists a population larger than 100 in the grid and 0 otherwise. The operation I use is
("lspop2010@1" > 100) * 1.
The output range is depicted in the picture below. Basically, the calculation produces a layer with no-data values only. Does anyone know the source of this problem?