# v-fold cross-validation
# (copied from rsample package, with edits for >7-class classification)
#' @import rsample
#' @importFrom tidyselect vars_select
#' @importFrom rlang enquo
vfold_cv <- function(data, v = 10, repeats = 1, strata = NULL, breaks = 4,
...) {
if(!missing(strata)) {
strata <- vars_select(names(data), !!enquo(strata))
if(length(strata) == 0) strata <- NULL
}
strata_check(strata, names(data))
if (repeats == 1) {
split_objs <- vfold_splits(data = data, v = v, strata = strata,
breaks = breaks)
} else {
for (i in 1:repeats) {
tmp <- vfold_splits(data = data, v = v, strata = strata)
tmp$id2 <- tmp$id
tmp$id <- names0(repeats, "Repeat")[i]
split_objs <- if (i == 1)
tmp
else
rbind(split_objs, tmp)
}
}
## We remove the holdout indicies since it will save space and we can
## derive them later when they are needed.
split_objs$splits <- map(split_objs$splits, rm_out)
## Save some overall information
cv_att <- list(v = v, repeats = repeats, strata = !is.null(strata))
new_rset(splits = split_objs$splits,
ids = split_objs[, grepl("^id", names(split_objs))],
attrib = cv_att,
subclass = c("vfold_cv", "rset"))
}
# Get the indices of the analysis set from the assessment set
vfold_complement <- function(ind, n) {
list(analysis = setdiff(1:n, ind),
assessment = ind)
}
#' @import rsample
#' @importFrom tibble tibble
#' @importFrom purrr map
#' @importFrom dplyr bind_rows
vfold_splits <- function(data, v = 10, strata = NULL, breaks = 4) {
if (!is.numeric(v) || length(v) != 1)
stop("`v` must be a single integer.", call. = FALSE)
n <- nrow(data)
if (is.null(strata)) {
folds <- sample(rep(1:v, length.out = n))
idx <- seq_len(n)
indices <- split(idx, folds)
} else {
stratas <- tibble::tibble(idx = 1:n,
strata = make_strata(getElement(data, strata),
breaks = breaks,
pool = 0.1))
stratas <- split(stratas, stratas$strata)
stratas <- purrr::map(stratas, add_vfolds, v = v)
stratas <- dplyr::bind_rows(stratas)
indices <- split(stratas$idx, stratas$folds)
}
indices <- lapply(indices, vfold_complement, n = n)
split_objs <- purrr::map(indices, make_splits, data = data,
class = "vfold_split")
tibble::tibble(splits = split_objs,
id = names0(length(split_objs), "Fold"))
}
add_vfolds <- function(x, v) {
x$folds <- sample(rep(1:v, length.out = nrow(x)))
x
}
strata_check <- function(strata, vars) {
if (!is.null(strata)) {
if (!is.character(strata) | length(strata) != 1)
stop("`strata` should be a single character value", call. = FALSE)
if (!(strata %in% vars))
stop(strata, " is not in `data`")
}
invisible(NULL)
}
make_splits <- function(ind, data, class = NULL) {
res <- rsplit(data, ind$analysis, ind$assessment)
if (!is.null(class))
res <- add_class(res, class)
res
}
rsplit <- function(data, in_id, out_id) {
if (!is.data.frame(data) & !is.matrix(data))
stop("`data` must be a data frame.", call. = FALSE)
if (!is.integer(in_id) | any(in_id < 1))
stop("`in_id` must be a positive integer vector.", call. = FALSE)
if(!all(is.na(out_id))) {
if (!is.integer(out_id) | any(out_id < 1))
stop("`out_id` must be a positive integer vector.", call. = FALSE)
}
if (length(in_id) == 0)
stop("At least one row should be selected for the analysis set.",
call. = FALSE)
structure(
list(
data = data,
in_id = in_id,
out_id = out_id
),
class = "rsplit"
)
}
add_class <- function(x, cls, at_end = TRUE) {
class(x) <- if (at_end)
c(class(x), cls)
else
c(cls, class(x))
x
}
names0 <- function (num, prefix = "x") {
if (num < 1)
stop("`num` should be > 0", call. = FALSE)
ind <- format(1:num)
ind <- gsub(" ", "0", ind)
paste0(prefix, ind)
}
## This will remove the assessment indices from an rsplit object
rm_out <- function(x) {
x$out_id <- NA
x
}
#' @importFrom tibble is_tibble as_tibble tibble
#' @importFrom dplyr bind_cols
# `splits`` should be either a list or a tibble with a single column
# called "splits"
# `ids`` should be either a character vector or a tibble with
# one or more columns that begin with "id"
new_rset <- function(splits, ids, attrib = NULL,
subclass = character()) {
stopifnot(is.list(splits))
if (!is_tibble(ids)) {
ids <- tibble(id = ids)
} else {
if (!all(grepl("^id", names(ids))))
stop("The `ids` tibble column names should start with 'id'",
call. = FALSE)
}
either_type <- function(x)
is.character(x) | is.factor(x)
ch_check <- vapply(ids, either_type, c(logical = TRUE))
if(!all(ch_check))
stop("All ID columns should be character or factor ",
"vectors.", call. = FALSE)
if (!is_tibble(splits)) {
splits <- tibble(splits = splits)
} else {
if(ncol(splits) > 1 | names(splits)[1] != "splits")
stop("The `splits` tibble should have a single column ",
"named `splits`.", call. = FALSE)
}
if (nrow(ids) != nrow(splits))
stop("Split and ID vectors have different lengths.",
call. = FALSE)
# Create another element to the splits that is a tibble containing
# an identifer for each id column so that, in isolation, the resample
# id can be known just based on the `rsplit` object. This can then be
# accessed using the `labels` methof for `rsplits`
splits$splits <- map2(splits$splits, split(ids, 1:nrow(ids)), add_id)
res <- bind_cols(splits, ids)
if (!is.null(attrib)) {
if (any(names(attrib) == ""))
stop("`attrib` should be a fully named list.",
call. = FALSE)
for (i in names(attrib))
attr(res, i) <- attrib[[i]]
}
if (length(subclass) > 0)
res <- add_class(res, cls = subclass, at_end = FALSE)
res
}
add_id <- function(split, id) {
split$id <- id
split
}
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.