# zonal: Zonal statistics In raster: Geographic Data Analysis and Modeling

 zonal R Documentation

## Zonal statistics

### Description

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)

### Usage

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

## S4 method for signature '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 `cellStats` for 'global' statistics (i.e., all of `x` is considered a single zone), and `extract` for summarizing values for polygons

### Examples

```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)

## End(Not run)

# multiple layers
zonal(stack(r, r*10), z, 'sum')
```

raster documentation built on Sept. 19, 2022, 1:05 a.m.