Document essential complexity of setDT#6756
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MichaelChirico merged 1 commit intomasterfrom Jan 24, 2025
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## master #6756 +/- ##
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Coverage 98.62% 98.62%
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tdhock
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Jan 24, 2025
| When working on large \code{lists} or \code{data.frames}, it might be both time and memory consuming to convert them to a \code{data.table} using \code{as.data.table(.)}, as this will make a complete copy of the input object before to convert it to a \code{data.table}. The \code{setDT} function takes care of this issue by allowing to convert \code{lists} - both named and unnamed lists and \code{data.frames} \emph{by reference} instead. That is, the input object is modified in place, no copy is being made. | ||
| When working on large \code{list}s or \code{data.frame}s, it might be both time- and memory-consuming to convert them to a \code{data.table} using \code{as.data.table(.)}, which will make a complete copy of the input object before converting it to a \code{data.table}. \code{setDT} takes care of this issue by converting any \code{list} (named or unnamed, data.frame or not) \emph{by reference} instead. That is, the input object is modified in place with no copy. | ||
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| This should come with low overhead, but note that \code{setDT} does check that the input is valid by looking for inconsistent input lengths and inadmissible column types (e.g. matrix). |
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great thanks, that explains why it is linear time in the number of columns.
jangorecki
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Jan 25, 2025
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There is a PR with light setDT where checks can be omitted - default false
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Closes #6741