cell-index-raster-abstraction.Rmd

---
title: "The raster functions for cell abstraction"
author: "Michael Sumner"
date: "`r Sys.Date()`"
output: rmarkdown::html_vignette
vignette: >
  %\VignetteIndexEntry{Raster Abstraction Functions}
  %\VignetteEngine{knitr::rmarkdown}
  %\VignetteEncoding{UTF-8}
---

The following functions in the `raster` package are designed to work with cell indexes. 

`fun(r, cell)`

* `[`
* `adjacent`
* `colFromCell`
* `extentFromCells`
* `rasterFromCells`
* `rowColFromCell`	
* `rowFromCell`
* `validCell`
* `xyFromCell`
* `xFromCell`
* `yFromCell`

The following functions will return cell indexes. 

`fun(r, query)` to return cells

* `cellFromCol`
* `cellFromLine`
* `cellFromPolygon`
* `cellFromRow`
* `cellFromRowCol`
* `cellFromRowColCombine`
* `cellFromXY`
* `cellsFromExtent`
* `fourCellsFromXY`

Others

* `setValues` will work as `fun(r, vals, index)` only for `RasterLayerSparse`
* `extent(Raster, r1, r2, c1, c2)` to crop an extent by row/column