# Ops.zonal_stat: Zonal statistics for raster maps In ursa: Non-Interactive Spatial Tools for Raster Processing and Visualization

 zonal_stat R Documentation

## Zonal statistics for raster maps

### Description

'Zonal' operator of map algebra. Applied to raster images.

### Usage

```zonal_stat(x, by, FUN, table = FALSE)

## S3 method for class 'ursaRaster'
aggregate(x, by, FUN, table = FALSE, ...)

```

### Arguments

 `x` `ursaRaster` object. Image for analysis. `by` `ursaRaster` object. Image of grouping elements. `FUN` a function to compute the summary statistics which can be applied to all data subsets. `table` Logical. If `table=TRUE` then summary statistics for each group is returned. The statistics is defined by `FUN`. If `stat=FALSE` then result is presented as `ursaRaster` object. `...` Other arguments which passed to function `aggregate` of package stats

### Details

`zonal_stat` is a wrapper of `aggregate(x,by,FUN,table=FALSE,na.rm=TRUE)`

You can use multichannel image (argument `x`) for analysis.

You can use multichannel raster image for group elements (argument `by`)

### Value

If `table=FALSE` then `ursaRaster` object of summarized statistics.
If `table=TRUE` then `data.frame`.

### Author(s)

Nikita Platonov platonov@sevin.ru

### Examples

```session_grid(NULL)
session_grid(regrid(mul=1/2))
a <- pixelsize()
val <- c(normal=a,half=a/2)
gr <- c(group=colorize(a,nbreak=1))#+0
print(as.table(gr))
##~ display(gr)
ra <- round(aggregate(val,gr,mean),4)
print(ra)
print(as.table(ra[1]))
print(as.table(ra[2]))
da <- aggregate(val,gr,table=TRUE,mean)
n <- aggregate(a,gr,table=TRUE,length)[,2,drop=FALSE]
da <- cbind(da,n=unname(n))
gr2 <- c(group2=colorize(a,nbreak=6))#+0
mgr <- list(gr,gr2)
da2 <- aggregate(val[1],mgr,table=TRUE,mean)
print(da2)
da3 <- aggregate(val,mgr,table=TRUE,mean)
print(da3)
ra3 <- aggregate(val,mgr,table=FALSE,mean) ## not implemented for rasters
print(ra3)
```

ursa documentation built on Dec. 28, 2022, 2:18 a.m.