# simulating variation in grid statistics
# when resampling from the same grid
#' Resample constructs
#'
#' The goal of resampling is to build variations of a single grid.
#' Two variants are implemented: The first is the \emph{leave-n-out} approach which
#' builds all possible grids when dropping n constructs. The second is a
#' \emph{bootstrap} approach, randomly drawing n constructs from the grid.
#'
#' @param n Number of constructs to drop or to sample in each generated grid. Defaults
#' to 1 for `grids_leave_n_out` and to the number of constructs for
#' `grids_bootstrap`.
#' @return List of grids.
#' @export
#' @rdname resampling
#'
grids_leave_n_out <- function(x, n = 1)
{
nc <- getNoOfConstructs(x) # size construct system
prop <- n / nc # proportion left out
if (prop > .4)
warning("Be aware that you leave more than 40% or more of the constructs", call. = FALSE)
n.subset <- nc - n
l <- combn(seq_len(nc), n.subset, simplify = F) # list of subset indexes
l <- lapply(l, function(i, x) x[i, ], x = x)
as.repgridlist(l)
}
#' @param reps Number of grids to generate.
#' @param replace Resample constructs with replacement?
#' @export
#' @rdname resampling
#'
grids_bootstrap <- function(x, n = nrow(x), reps = 100, replace = TRUE)
{
nc <- getNoOfConstructs(x) # size construct system
prop <- n / nc # proportion to sample
if (prop < .6)
warning("Be aware that you resample less than 60% of the constructs", call. = FALSE)
l_i <- replicate(reps, sample(seq_len(nc), n, replace = replace), simplify = FALSE)
l <- lapply(l_i, function(i, x) x[i, ], x = x)
as.repgridlist(l)
}
#' Number of constructs and elements for grids in repgridlist
#' @return Numeric vector with the number of constructs or elements
#' of each grid in repgridlist object.
#' @export
#' @keywords internal
nrow.repgridlist <- function(x) {
vapply(x, nrow, numeric(1))
}
#' @export
#' @keywords internal
ncol.repgridlist <- function(x) {
vapply(x, ncol, numeric(1))
}
#### testing / examples ------------------------------------------------------
library(OpenRepGrid)
library(tidyverse)
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