I correct myself. Obviously, the line
first[is.na(first) | isFALSE(first)] <- FALSE
should read
first[is.na(first)] <- FALSE
Serguei.
Le 25/04/2023 à 11:30, Serguei Sokol a écrit :
Le 25/04/2023 à 10:24, Viechtbauer, Wolfgang (NP) a écrit :
Hi all,
Posted this many years ago
(https://stat.ethz.ch/pipermail/r-devel/2017-December/075224.html),
but either this slipped under the radar or my feeble mind is unable
to understand what xyTable() is doing here and nobody bothered to
correct me. I now stumbled again across this issue.
x <- c(1, 1, 2, 2, 2, 3)
y <- c(1, 2, 1, 3, NA, 3)
table(x, y, useNA="always")
xyTable(x, y)
Why does xyTable() report that there are NA instances of (2,3)? I
could understand the logic that the NA could be anything, including a
3, so the $number value for (2,3) is therefore unknown, but then the
same should apply so (2,1), but here $number is 1, so the logic is
then inconsistent.
I stared at the xyTable code for a while and I suspect this is coming
from order() using na.last=TRUE by default, but in any case, to me
the behavior above is surprising.
Not really. The variable 'first' in xyTable() is supposed to detect
positions of first values in repeated pair sequences. Then it is used
to retained only their indexes in a vector of type 1:n. Finally, by
taking diff(), a number of repeated pairs is obtained. However, as
'first' will contain one NA for your example, the diff() call will
produce two NAs by taking the difference with precedent and following
number. Hence, the result.
Here is a slightly modified code ox xyTable to handle NA too.
xyTableNA <- function (x, y = NULL, digits)
{
x <- xy.coords(x, y, setLab = FALSE)
y <- signif(x$y, digits = digits)
x <- signif(x$x, digits = digits)
n <- length(x)
number <- if (n > 0) {
orderxy <- order(x, y)
x <- x[orderxy]
y <- y[orderxy]
first <- c(TRUE, (x[-1L] != x[-n]) | (y[-1L] != y[-n]))
firstNA <- c(TRUE, xor(is.na(x[-1L]), is.na(x[-n])) |
xor(is.na(y[-1L]), is.na(y[-n])))
first[firstNA] <- TRUE
first[is.na(first) | isFALSE(first)] <- FALSE
x <- x[first]
y <- y[first]
diff(c((1L:n)[first], n + 1L))
}
else integer()
list(x = x, y = y, number = number)
}
Best,
Serguei.
Best,
Wolfgang
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Serguei Sokol
Ingenieur de recherche INRAE
Cellule Mathématiques
TBI, INSA/INRAE UMR 792, INSA/CNRS UMR 5504
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email: so...@insa-toulouse.fr
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