This method returns the size of the simulated tissue.
Examples
# set the seed of the random number generator
set.seed(0)
# create a simulation having size 1200x900
sim <- SpatialSimulation(width=1200, height=900)
# get the tissue size, i.e., expecting c(1200,900)
sim$get_tissue_size()
#> [1] 1200 900