extract: Extraction of values from multiple RasterLayers in a...
In chronosphere: Earth System History Variables

Description Usage Arguments Format Value Examples

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

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)

`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 `RasterLayer`s 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 `RasterLayer`s 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.

An object of class standardGeneric of length 1.

A numeric vector, matrix or array of values.

# 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)