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#' Spread a key-value pair across multiple columns
#'
#' @description
#' `r lifecycle::badge("superseded")`
#'
#' Development on `spread()` is complete, and for new code we recommend
#' switching to `pivot_wider()`, which is easier to use, more featureful, and
#' still under active development.
#' `df %>% spread(key, value)` is equivalent to
#' `df %>% pivot_wider(names_from = key, values_from = value)`
#'
#' See more details in `vignette("pivot")`.
#'
#' @param data A data frame.
#' @param key,value <[`tidy-select`][tidyr_tidy_select]> Columns to use
#' for `key` and `value`.
#' @param fill If set, missing values will be replaced with this value. Note
#' that there are two types of missingness in the input: explicit missing
#' values (i.e. `NA`), and implicit missings, rows that simply aren't
#' present. Both types of missing value will be replaced by `fill`.
#' @param convert If `TRUE`, [type.convert()] with \code{asis =
#' TRUE} will be run on each of the new columns. This is useful if the value
#' column was a mix of variables that was coerced to a string. If the class of
#' the value column was factor or date, note that will not be true of the new
#' columns that are produced, which are coerced to character before type
#' conversion.
#' @param drop If `FALSE`, will keep factor levels that don't appear in the
#' data, filling in missing combinations with `fill`.
#' @param sep If `NULL`, the column names will be taken from the values of
#' `key` variable. If non-`NULL`, the column names will be given
#' by `"<key_name><sep><key_value>"`.
#' @export
#' @examples
#' stocks <- tibble(
#' time = as.Date("2009-01-01") + 0:9,
#' X = rnorm(10, 0, 1),
#' Y = rnorm(10, 0, 2),
#' Z = rnorm(10, 0, 4)
#' )
#' stocksm <- stocks %>% gather(stock, price, -time)
#' stocksm %>% spread(stock, price)
#' stocksm %>% spread(time, price)
#'
#' # Spread and gather are complements
#' df <- tibble(x = c("a", "b"), y = c(3, 4), z = c(5, 6))
#' df %>%
#' spread(x, y) %>%
#' gather("x", "y", a:b, na.rm = TRUE)
#'
#' # Use 'convert = TRUE' to produce variables of mixed type
#' df <- tibble(
#' row = rep(c(1, 51), each = 3),
#' var = rep(c("Sepal.Length", "Species", "Species_num"), 2),
#' value = c(5.1, "setosa", 1, 7.0, "versicolor", 2)
#' )
#' df %>% spread(var, value) %>% str()
#' df %>% spread(var, value, convert = TRUE) %>% str()
spread <- function(data, key, value, fill = NA, convert = FALSE,
drop = TRUE, sep = NULL) {
UseMethod("spread")
}
#' @export
spread.data.frame <- function(data, key, value, fill = NA, convert = FALSE,
drop = TRUE, sep = NULL) {
key_var <- tidyselect::vars_pull(names(data), !!enquo(key))
value_var <- tidyselect::vars_pull(names(data), !!enquo(value))
col <- data[key_var]
col_id <- id(col, drop = drop)
col_labels <- split_labels(col, col_id, drop = drop)
rows <- data[setdiff(names(data), c(key_var, value_var))]
if (ncol(rows) == 0 && nrow(rows) > 0) {
# Special case when there's only one row
row_id <- structure(1L, n = 1L)
row_labels <- as.data.frame(matrix(nrow = 1, ncol = 0))
} else {
row_id <- id(rows, drop = drop)
row_labels <- split_labels(rows, row_id, drop = drop)
rownames(row_labels) <- NULL
}
overall <- id(list(col_id, row_id), drop = FALSE)
n <- attr(overall, "n")
# Check that each output value occurs in unique location
if (anyDuplicated(overall)) {
groups <- split(seq_along(overall), overall)
groups <- groups[map_int(groups, length) > 1]
shared <- sum(map_int(groups, length))
str <- map_chr(groups, function(x) paste0(x, collapse = ", "))
cli::cli_abort(c(
"Each row of output must be identified by a unique combination of keys.",
i = "Keys are shared for {shared} rows",
set_names(str, "*")
))
}
# Add in missing values, if necessary
if (length(overall) < n) {
overall <- match(seq_len(n), overall, nomatch = NA)
} else {
overall <- order(overall)
}
value <- data[[value_var]]
ordered <- value[overall]
if (!is.na(fill)) {
ordered[is.na(ordered)] <- fill
}
if (convert && !is_character(ordered)) {
ordered <- as.character(ordered)
}
dim(ordered) <- c(attr(row_id, "n"), attr(col_id, "n"))
colnames(ordered) <- enc2utf8(col_names(col_labels, sep = sep))
ordered <- as_tibble_matrix(ordered)
if (convert) {
ordered[] <- map(ordered, type.convert, as.is = TRUE)
}
out <- df_append(row_labels, ordered)
reconstruct_tibble(data, out, c(key_var, value_var))
}
col_names <- function(x, sep = NULL) {
names <- as.character(x[[1]])
if (is_null(sep)) {
if (length(names) == 0) {
# ifelse will return logical()
character()
} else {
ifelse(are_na(names), "<NA>", names)
}
} else {
paste(names(x)[[1]], names, sep = sep)
}
}
as_tibble_matrix <- function(x) {
# getS3method() only available in R >= 3.3
get("as_tibble.matrix", asNamespace("tibble"), mode = "function")(x)
}
split_labels <- function(df, id, drop = TRUE) {
if (length(df) == 0) {
return(df)
}
if (drop) {
representative <- match(sort(unique(id)), id)
out <- df[representative, , drop = FALSE]
rownames(out) <- NULL
out
} else {
unique_values <- map(df, ulevels)
rev(expand.grid(rev(unique_values), stringsAsFactors = FALSE))
}
}
ulevels <- function(x) {
if (is.factor(x)) {
orig_levs <- levels(x)
x <- addNA(x, ifany = TRUE)
levs <- levels(x)
factor(levs, levels = orig_levs, ordered = is.ordered(x), exclude = NULL)
} else if (is.list(x)) {
unique(x)
} else {
sort(unique(x), na.last = TRUE)
}
}
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