ExtractTile: Extract subset tiles from bigger tiles of MODIS data.

In seantuck12/MODISTools: MODIS Subsetting Tools

Description

Input a dataset of MODIS data, comprised of one or many tiles of pixels - a column for each pixel in a tile and a row for each tile - and extract a nested subset from within these tiles.

Usage

ExtractTile(Data, Rows, Cols, Grid=FALSE)

Arguments

Data	Numeric vector, matrix, or data frame; The input data, containing the large tile(s) that smaller tiles will be extracted from. If a matrix or data frame, each row should represent a distinct tile, whilst each column in a row will be a different pixel within the that tile.
Rows	Numeric - two integers; Rows[1] should be the number of rows in the large tile(s) of pixels. Rows[2] is the number of rows you would like either side of the tile(s) central pixel in the small tile(s) output.
Cols	Numeric - two integers; Cols[1] should be the number of columns in the large tile(s) of pixels. Cols[2] is the number of columns you would like either side of the tile(s) central pixel in the small tile(s) output.
Grid	Logical; if Grid=FALSE, the smaller tile(s) will be in a matrix, like the input. If Grid=TRUE, the output will be an array, with tile(s) presented explicitly. See value.

Details

Data should only include MODIS data and not any other metadata for the input tiles (see example). Rows[2] and Cols[2] should equate to a nested subset of Rows[1] and Cols[1]. Rows[1] and Cols[1] specify the dimensions of the tiles, laid out in rows in matrix, and therefore should equate to the dimensions of a matrix that is filled by ncols(Data) data points.

Value

The output may have two possible structures, optionally chosen with the Grid argument. If Grid=FALSE, the output will be the same structure as the input - a nxm matrix, where n is the number of tiles and m is the number of pixels in each tile - with the same number of rows but only the number of pixels in the smaller tile(s) for each row. If Grid=TRUE, the output will be an array, with the tiles laid out with pixels in spatial order - a matrix of the subset of pixels, for each row in Data.

Author(s)

Sean Tuck

Examples

## Not run:  # dontrun() used because running the example requires internet access.
data(SubsetExample)
MODISSubsets(LoadDat = SubsetExample, Products = "MOD13Q1", 
    Bands = c("250m_16_days_EVI", "250m_16_days_pixel_reliability"), Size = c(1,1), 
    StartDate = FALSE, TimeSeriesLength = 1)
MODISSummaries(LoadDat = SubsetExample, Product = "MOD13Q1", Bands = "250m_16_days_EVI", 
    ValidRange = c(-2000,10000), NoDataFill = -3000, ScaleFactor = 0.0001,
    StartDate = FALSE, QualityScreen = TRUE, QualityThreshold = 0,
    QualityBand = "250m_16_days_pixel_reliability")

if(sum(grepl("MODIS_Data", list.files())) != 1){
  print("Could not identify 'MODIS_Data' csv output file from MODISSummaries")
} else {
  TileExample <- read.csv(list.files(pattern = "MODIS_Data"))
  TileExample <- TileExample[1,which(grepl("pixel", names(TileExample)))]
  
  dim(TileExample)
  dim(ExtractTile(Data = TileExample, Rows = c(9,2), Cols = c(9,2), Grid = FALSE))
  ExtractTile(Data = TileExample, Rows = c(9,2), Cols = c(9,2), Grid = FALSE)
  
  matrix(TileExample, nrow = 9, ncol = 9, byrow = TRUE)
  ExtractTile(Data = TileExample, Rows = c(9,2), Cols = c(9,2), Grid = TRUE)
}
  
## End(Not run)

seantuck12/MODISTools documentation built on May 29, 2019, 4:55 p.m.