# zonal

##### Zonal statistics

Compute zonal statistics, that is summarized values of a Raster* object for each "zone" defined by a RasterLayer.

If `stat`

is a true `function`

, `zonal`

will fail (gracefully) for very large Raster objects, but it will in most cases work for functions that can be defined as by a character argument ('mean', 'sd', 'min', 'max', or 'sum'). In addition you can use 'count' to count the number of cells in each zone (only useful with `na.rm=TRUE`

, otherwise `freq(z)`

would be more direct.

If a function is used, it should accept a `na.rm`

argument (or at least a `...`

argument)

- Keywords
- spatial

##### Usage

```
# S4 method for RasterLayer,RasterLayer
zonal(x, z, fun='mean', digits=0, na.rm=TRUE, ...)
```# S4 method for RasterStackBrick,RasterLayer
zonal(x, z, fun='mean', digits=0, na.rm=TRUE, ...)

##### Arguments

- x
Raster* object

- z
RasterLayer with codes representing zones

- fun
function to be applied to summarize the values by zone. Either as character: 'mean', 'sd', 'min', 'max', 'sum'; or, for relatively small Raster* objects, a proper function

- digits
integer. Number of digits to maintain in 'zones'. By default averaged to an integer (zero digits)

- na.rm
logical. If

`TRUE`

,`NA`

values in`x`

are ignored- ...
additional arguments. One implemented:

`progress`

, as in`writeRaster`

##### Value

A matrix with a value for each zone (unique value in `zones`

)

##### See Also

See `cellStats`

for 'global' statistics (i.e., all of `x`

is considered a single zone), and `extract`

for summarizing values for polygons

##### Examples

```
# NOT RUN {
r <- raster(ncols=10, nrows=10)
values(r) <- runif(ncell(r)) * 1:ncell(r)
z <- r
values(z) <- rep(1:5, each=20)
# for large files, use a character value rather than a function
zonal(r, z, 'sum')
# for smaller files you can also provide a function
# }
# NOT RUN {
zonal(r, z, mean)
zonal(r, z, min)
# }
# NOT RUN {
# multiple layers
zonal(stack(r, r*10), z, 'sum')
# }
```

*Documentation reproduced from package raster, version 3.1-5, License: GPL (>= 3)*