Select subset of a raster according to values

Question

I have one raster which is split in several patches, which one having a special ID, so each cell will be identified by the ID of the patch they belong. In the example below, I have 1180 patches. I calculated the area of all those patches and I'd like to select only those which are > 100 ha. Here is my code, but the problem is that R gives a vector at the end and not a raster containing only those patches with the criteria.

# list of ID of patches (hors NA)
  num_patches <- unique(raster[!is.na(raster[])]) # list length= 1180
  area_patches <- c()
  # calculate area
  for (pixel in num_patches){
    area_patches <- c(area_patches ,sum(raster[raster == pixel]) * res(raster)[1]^2)
  }
  # conversion des m² en ha
  area_patches <- area_patches/ha
  # identify patches > 100
  pos_patches_100ha <- which(area_patches >= 100)
  # select only patches > 100 ha
  raster <- raster[raster %in% pos_parche_100ha] --> selection doesn't work, the out isn't a raster but a vector