extract: Extraction of values from multiple RasterLayers in a...

Description Usage Arguments Format Value Examples

Description

The function takes a set of time-dependent coordinates and extracts the value they point to from associted RasterLayers in a RasterArray.

Usage

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extract

## S4 method for signature 'RasterArray,matrix'
extract(x, y)

## S4 method for signature 'RasterArray,data.frame'
extract(x, y, by = NULL, margin = 1, lng = "plng", lat = "plat", force = NULL)

Arguments

x

(RasterArray). A set of RasterLayers that are associated with entries (one dimension) or the rows of x.

y

(matrix or data.frame). The data table containing the coordinates and (optionally) the indices or names of the associated RasterLayers in x.

by

(character or vector) In case of a data.frame input, the link between x and y. If by is a character string then it is expected to be column of x and should contain the names or the indices of the associated RasterLayers in x. If it is a vector its length should match the number of rows in x and it will be used as if it were a column of x.

margin

(numeric) A single value describing which margin (dimension of x) by is referring to (1: rows, 2: columns, etc.).

lng

(character) A column of x that includes the paleolongitudes.

lat

(character) A column of x that includes the paleolatitudes.

force

(character) If set to "numeric" the by argument or the column it points to will be converted to numeric values, and x will be subsetted with numeric subscripts of the x RasterArray. If set to "character", the by column (or vector) will be forced to character values and will be used as character subscripts.

Format

An object of class standardGeneric of length 1.

Value

A numeric vector, matrix or array of values.

Examples

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# one pair of random coordinates from Africa
mat <- matrix(c(                
  -1.34, 42.96
), ncol=2, byrow=TRUE) 

# repeat four times
mat<- mat[rep(1,4), ]

# assign default names and age
df<- data.frame(plng=mat[, 1],plat=mat[, 2], age=c(1,3,5, 1))
rownames(df) <- paste("point", 1:nrow(df))

# first coordinate pair will be extrated from RasterLayer 1 ["0"]
# second coordinate pair will be extracted from RasterLayer 3 ["10"]
# thrid coordinate pair will be extracted from RasterLayer 5 ["20"]
# fourth coordinate pair will be extracted from RasterLayer 1 ["0"]
data(dems)
extract(dems, df, by="age")

# by=NULL will be implemented in the next update 
# (all coordinates extracted from all layers)

chronosphere documentation built on April 19, 2021, 1:07 a.m.