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jangorecki merged 1 commit into from
Nov 24, 2025
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?fwrite: replace a dead link with a snapshot #7437

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2 changes: 1 addition & 1 deletion man/fwrite.Rd
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Expand Up @@ -66,7 +66,7 @@ fwrite(x, file = "", append = FALSE, quote = "auto",
\item{forceDecimal}{ Should decimal points be forced for whole numbers in numeric columns? When \code{FALSE}, the default, whole numbers like \code{c(1.0, 2.0, 3.0)} will be written as \samp{1, 2, 3} i.e., dropping \code{dec}. }
}
\details{
\code{fwrite} began as a community contribution with \href{https://github.com/Rdatatable/data.table/pull/1613}{pull request #1613} by Otto Seiskari. This gave Matt Dowle the impetus to specialize the numeric formatting and to parallelize: \url{https://h2o.ai/blog/2016/fast-csv-writing-for-r/}. Final items were tracked in \href{https://github.com/Rdatatable/data.table/issues/1664}{issue #1664} such as automatic quoting, \code{bit64::integer64} support, decimal/scientific formatting exactly matching \code{write.csv} between 2.225074e-308 and 1.797693e+308 to 15 significant figures, \code{row.names}, dates (between 0000-03-01 and 9999-12-31), times and \code{sep2} for \code{list} columns where each cell can itself be a vector.
\code{fwrite} began as a community contribution with \href{https://github.com/Rdatatable/data.table/pull/1613}{pull request #1613} by Otto Seiskari. This gave Matt Dowle the impetus to specialize the numeric formatting and to parallelize: \url{https://web.archive.org/web/20250623031725/https://h2o.ai/blog/2016/fast-csv-writing-for-r/}. Final items were tracked in \href{https://github.com/Rdatatable/data.table/issues/1664}{issue #1664} such as automatic quoting, \code{bit64::integer64} support, decimal/scientific formatting exactly matching \code{write.csv} between 2.225074e-308 and 1.797693e+308 to 15 significant figures, \code{row.names}, dates (between 0000-03-01 and 9999-12-31), times and \code{sep2} for \code{list} columns where each cell can itself be a vector.

To save space, \code{fwrite} prefers to write wide numeric values in scientific notation -- e.g. \code{10000000000} takes up much more space than \code{1e+10}. Most file readers (e.g. \code{\link{fread}}) understand scientific notation, so there's no fidelity loss. Like in base R, users can control this by specifying the \code{scipen} argument, which follows the same rules as \code{\link[base]{options}('scipen')}. \code{fwrite} will see how much space a value will take to write in scientific vs. decimal notation, and will only write in scientific notation if the latter is more than \code{scipen} characters wider. For \code{10000000000}, then, \code{1e+10} will be written whenever \code{scipen<6}.

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