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Merged
mattdowle merged 2 commits into from
Aug 28, 2021
Merged

dcast(empty) returns empty #5118

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7660d39
dcast(empty) returns empty
mattdowle Aug 28, 2021
93fb636
empty result is keyed, good
mattdowle Aug 28, 2021
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2 changes: 2 additions & 0 deletions NEWS.md
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Expand Up @@ -350,6 +350,8 @@
#
# remaining 99,987 of these 100,000 were already identical
```

41. `dcast(empty-DT)` now returns an empty `data.table` rather than error `Cannot cast an empty data.table`, [#1215](https://github.com/Rdatatable/data.table/issues/1215). Thanks to Damian Betebenner for reporting, and Matt Dowle for fixing.

## NOTES

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1 change: 0 additions & 1 deletion R/fcast.R
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Expand Up @@ -151,7 +151,6 @@ dcast.data.table = function(data, formula, fun.aggregate = NULL, sep = "_", ...,
idx = which(eval(subset, data, parent.frame())) # any advantage thro' secondary keys?
dat = .Call(CsubsetDT, dat, idx, seq_along(dat))
}
if (!nrow(dat) || !ncol(dat)) stopf("Can not cast an empty data.table")
fun.call = m[["fun.aggregate"]]
fill.default = NULL
if (is.null(fun.call)) {
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3 changes: 1 addition & 2 deletions inst/tests/tests.Rraw
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Expand Up @@ -13717,8 +13717,7 @@ test(1962.086, dcast(DT, a ~ a, drop = NA),
DT = data.table(a = c(1, 1, 2, 2), b = list(1, 2, 3, 4), c = c(4, 4, 2, 2))
test(1962.087, dcast(DT, a ~ b, value.var = 'b'),
error = 'Columns specified in formula can not be of type list')
test(1962.088, dcast(DT[0L, ], a ~ c, value.var = 'b'),
error = 'Can not cast an empty data.table')
test(1962.088, dcast(DT[0L, ], a ~ c, value.var = 'b'), data.table(a=numeric(), key="a")) #1215
test(1962.089, dcast(DT, a ~ c, value.var = 'b'),
data.table(a = c(1, 2), `2` = c(0L, 2L), `4` = c(2L, 0L), key = 'a'),
message = 'Aggregate function missing')
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