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Is there a function to return the number of groups? #477

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Mullefa opened this issue Jul 1, 2014 · 1 comment
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Is there a function to return the number of groups? #477

Mullefa opened this issue Jul 1, 2014 · 1 comment
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@Mullefa
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@Mullefa Mullefa commented Jul 1, 2014

Wasn't sure if there was. Currently I'm using this function:

n_groups <- function(tbl) {
  g <- groups(tbl)

  if (is.null(g)) {
    tbl_nm <- deparse(substitute(tbl))
    warning(tbl_nm, " is not grouped", immediate. = TRUE)
    0
  } else {
    g <- unlist(lapply(g, as.character))
    nrow(unique(tbl[, g, drop = FALSE]))
  }
}
@hadley
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@hadley hadley commented Jul 28, 2014

Could you please give me an example of where you need this?

@hadley hadley added this to the 0.3 milestone Aug 1, 2014
@hadley hadley self-assigned this Aug 1, 2014
@hadley hadley closed this in cc0026a Aug 1, 2014
krlmlr pushed a commit to krlmlr/dplyr that referenced this issue Mar 2, 2016
Also make sure group_size works for ungrouped data, and add tests
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