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#' @title Peek at values and type of variables in a data frame
#' @name data_peek
#'
#' @description This function creates a table a data frame, showing all
#' column names, variable types and the first values (as many as fit into
#' the screen).
#'
#' @param x A data frame.
#' @param width Maximum width of line length to display. If `NULL`, width will
#' be determined using `options()$width`.
#' @param ... not used.
#' @inheritParams extract_column_names
#'
#' @note To show only specific or a limited number of variables, use the
#' `select` argument, e.g. `select = 1:5` to show only the first five variables.
#'
#' @return A data frame with three columns, containing information about
#' the name, type and first values of the input data frame.
#'
#' @examples
#' data(efc)
#' data_peek(efc)
#' # show variables two to four
#' data_peek(efc, select = 2:4)
#' @export
data_peek <- function(x, ...) {
UseMethod("data_peek")
}
#' @rdname data_peek
#' @export
data_peek.data.frame <- function(x,
select = NULL,
exclude = NULL,
ignore_case = FALSE,
regex = FALSE,
width = NULL,
verbose = TRUE,
...) {
# evaluate arguments
select <- .select_nse(select,
x,
exclude,
ignore_case,
regex = regex,
verbose = verbose
)
out <- do.call(rbind, lapply(select, function(i) {
.data_peek(x, i, width, verbose = verbose, ...)
}))
class(out) <- c("dw_data_peek", class(out))
attr(out, "n_cols") <- ncol(x)
attr(out, "n_rows") <- nrow(x)
attr(out, "max_width") <- ifelse(is.null(width), 0.9 * options()$width, width)
out
}
# methods -----------------
#' @export
print.dw_data_peek <- function(x, ...) {
x <- format(x, ...)
caption <- sprintf(
"Data frame with %i rows and %i variables",
attributes(x)$n_rows,
attributes(x)$n_cols
)
cat(insight::export_table(x, align = "lll", caption = caption, ...))
}
#' @export
print_md.dw_data_peek <- function(x, ...) {
x <- format(x, ...)
caption <- sprintf(
"Data frame with %i rows and %i variables",
attributes(x)$n_rows,
attributes(x)$n_cols
)
insight::export_table(x, align = "lll", format = "markdown", caption = caption, ...)
}
#' @export
print_html.dw_data_peek <- function(x, ...) {
x <- format(x, ...)
caption <- sprintf(
"Data frame with %i rows and %i variables",
attributes(x)$n_rows,
attributes(x)$n_cols
)
insight::export_table(x, align = "lll", format = "html", caption = caption, ...)
}
#' @export
format.dw_data_peek <- function(x, ...) {
width_col1 <- max(nchar(x$Variable))
width_col2 <- max(nchar(x$Type))
max_width <- attributes(x)$max_width
if (is.null(max_width)) {
max_width <- 0.9 * options()$width
}
width_col3 <- max_width - (width_col1 + width_col2 + 10) # 10 = separator chars in table
# shorten value-string
x$Values <- substr(x$Values, 0, width_col3)
# make sure we have a clear truncation, at last "comma"
x$Values <- gsub("(.+)(,.+)$", "\\1", x$Values)
# add "..."
x$Values <- paste0(x$Values, ", ...")
x
}
# helper -----------------
.data_peek <- function(x, variable, width = NULL, verbose = TRUE, ...) {
v_name <- variable
v_type <- .variable_type(x[[variable]])
v_type[v_type == "categorical"] <- "factor"
max_width <- ifelse(is.null(width), 0.9 * options()$width, width)
v_values <- toString(x[[variable]][1:max_width])
data.frame(Variable = v_name, Type = v_type, Values = v_values, stringsAsFactors = FALSE)
}
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