Please consider:
dt <- data.table(id = c("a", "a", "b", "b"),
var = c(1.1, 2.5, 6.3, 4.5),
key = "id")
#1.9.3 latest revision
dt["c", list(id, check = any(var > 3)), nomatch=0L]
# Error in if (mn%%n[i] != 0) warning("Item ", i, " is of size ", n[i], :
# missing value where TRUE/FALSE needed
#1.9.3 revision 1200 (last 'stable')
dt["c", list(check = any(var > 3)), nomatch=0L]
# Empty data.table (0 rows) of 2 cols: id,check
This happens only generating a brand-new column and not when simply selecting existing ones or when 'aggregation function' are not used. These
> dt["c", list(id, check = var), nomatch=0L]
Empty data.table (0 rows) of 2 cols: id,check
> dt["c", list(id, check = var > 3), nomatch=0L]
Empty data.table (0 rows) of 2 cols: id,check
evaluate as expected. This is caused from these lines of as.data.table.list function data.table.R:
n = vapply(x, length, 0L)
mn = max(n)
x = copy(x)
if (any(n<mn))
for (i in which(n<mn)) {
if (!is.null(x[[i]])) {# avoids warning when a list element is NULL
# Implementing FR #4813 - recycle with warning when nr %% nrows[i] != 0L
if (mn %% n[i] != 0)
warning("Item ", i, " is of size ", n[i], " but maximum size is ", mn, " (recycled leaving a remainder of ", mn%%n[i], " items)")
x[[i]] = rep(x[[i]], length.out=mn)
}
}
I believe the following happens:
x <- as.list(dt["c", list(id, var), nomatch=0L])
x$var <- max(x$var) # to simulate the internal process
n = vapply(x, length, 0L)
mn = max(n)
if (any(n<mn))
for (i in which(n<mn)) {
if (!is.null(x[[i]])) {# avoids warning when a list element is NULL
# Implementing FR #4813 - recycle with warning when nr %% nrows[i] != 0L
if (mn %% n[i] != 0) # <----------------- HERE
warning("Item ", i, " is of size ", n[i], " but maximum size is ", mn, " (recycled leaving a remainder of ", mn%%n[i], " items)")
x[[i]] = rep(x[[i]], length.out=mn)
}
}
# Error in if (mn%%n[i] != 0) warning("Item ", i, " is of size ", n[i], :
# missing value where TRUE/FALSE needed
1L %% 0L is NA, hence the error. In fact, if there are no zero length columns in the result it works
> dt["c", list(check = any(var > 3)), nomatch=0L]
check
1: FALSE
Even though I believe that the result of the last expression should be Empty data.table (0 rows) of 1 col: check. If any vector has zero length, can't as.data.table.list just set the table rows to zero? I don't think there is a case when a column has zero length and i evaluates to a positive (non zero) number of rows.
Thanks,
Michele.
Please consider:
This happens only generating a brand-new column and not when simply selecting existing ones or when 'aggregation function' are not used. These
evaluate as expected. This is caused from these lines of
as.data.table.listfunction data.table.R:I believe the following happens:
1L %% 0Lis NA, hence the error. In fact, if there are no zero length columns in the result it worksEven though I believe that the result of the last expression should be
Empty data.table (0 rows) of 1 col: check. If any vector has zero length, can'tas.data.table.listjust set the table rows to zero? I don't think there is a case when a column has zero length andievaluates to a positive (non zero) number of rows.Thanks,
Michele.