When subsetting a matrix or DF, it is possible to reference row columns, such as `df1[1:5, 3:10]`, or `df3[2:4, ]`. 

**Is there any way to do this with a raster? That is, can I clip just rows 500:700, for example from a raster object?**

I have tried using `rasterFromCells()`, but it doesn't give me the result I want (and it seems like there should be a more simple solution given R's other slick subsetting methods).

**Example:** 

```
r <- raster(ncols = 50, nrow = 50)
r[] <- 1:ncell(r)

# I would like to subset the bottom 50 rows of cells, but keep it as a raster.
# However, this returns a numeric object.
rSub <- r[30:50, 1:50]  

```

Thanks!