Helper to assign block numbers to data according to variables and limits

Usage

assign_blocks(data, variable_1, variable_2, n_cols, n_rows = NULL,
              xlb, ylb = NULL, block_type = "equal_area")

Arguments

data: matrix or data.frame that contains at least four columns: "Longitude" and "Latitude" to represent geographic position, and two other columns to represent the variables of the 2D environmental space.
variable_1: (character or numeric) name or position of the first variable (x-axis) to be used to create blocks.
variable_2: (character or numeric) name or position of the second variable (y-axis) to be used to create blocks (must be different from the first one).
n_cols: (numeric) number of columns of a grid used to create blocks and split the bi-dimensional space.
n_rows: (numeric) number of rows of a grid used to create blocks and split the bi-dimensional space. If NULL, the default, n_rows = n_cols.
xlb: (numeric) vector of values of extremes for all blocks considering variable_1.
ylb: (numeric) vector of values of extremes for all blocks considering variable_2. Needed when block_type = "equal_area". Default = NULL.
block_type: (character) type of blocks to be used for dividing the bi-dimensional space. Two options are available: "equal_area" and "equal_points". Default = "equal_area". Note that this option has important association regarding full representation of the extreme values of environmental variables across the study region.

Value

Original element defined in data plus a new column named "Block" defining the block that correspond to each of the points represented in rows.

Examples

# Data
dat <- matrix(runif(800), ncol = 4)
xlims <- quantile(dat[, 3])
ylims <- quantile(dat[, 4])

# Assigning blocks
datb <- assign_blocks(dat, variable_1 = 3, variable_2 = 4, n_cols = 10,
                      xlb = xlims, ylb = ylims, block_type = "equal_area")