getValuesBlock_stackfix: Get a block of raster cell values (optimization fix for...
In gearslaboratory/spatial.tools: R Functions for Working with Spatial Data

Description Usage Arguments Details Value Author(s) See Also Examples

View source: R/getValuesBlock_stackfix.R

A faster version of getValuesBlock for RasterStack.

1 2	getValuesBlock_stackfix(x, row = 1, nrows = 1, col = 1, ncols = (ncol(x) - col + 1), lyrs = (1:nlayers(x)))

`x`	Raster* object
`row`	positive integer. Row number to start from, should be between 1 and nrow(x)
`nrows`	postive integer. How many rows? Default is 1
`col`	postive integer. Column number to start from, should be between 1 and ncol(x)
`ncols`	postive integer. How many columns? Default is the number of colums left after the start column
`lyrs`	integer (vector). Which layers? Default is all layers (1:nlayers(x))

In certain cases, getValuesBlock may run very slowly on a RasterStack, particularly when the RasterStack is comprised of RasterBricks. This code attempts to fix the inefficiency by running the extract on each unique file of the RasterStack, rather than each unique layer.

matrix or vector (if (x=RasterLayer), unless format='matrix')

Jonathan A. Greenberg

getValuesBlock

library("raster")
tahoe_highrez <- brick(system.file("external/tahoe_highrez.tif", package="spatial.tools"))
tahoe_highrez_stack <- stack(tahoe_highrez,tahoe_highrez,tahoe_highrez)
# getValuesBlock stack extraction:
system.time(tahoe_highrez_extract <- getValuesBlock(tahoe_highrez_stack))
# getValuesBlock_stackfix stack extraction:
system.time(tahoe_highrez_extract <- getValuesBlock_stackfix(tahoe_highrez_stack))