Dear all,
I did some more tests regarding the == operator in Ops.data.frame (see
below). All tests done in R 3.6.1 (x86_64-w64-mingw32).
I find that errors are thrown also when comparing a zero length
data.frame to atomic objects with length>0 which should be a valid case
according to the documentation. This can be traced to a check in the
last line of Ops.data.frame which tests for the presence of an empty
result value (i.e. list() ) but does not handle a list of empty values
(i.e. list(logical(0))) which in fact is generated in those cases. There
is a simple fix (see also below).
There are other issues with the S4 class example (i.e. data.frame() ==
) which fails for different reasons.
##
d_0 = data.frame(a = numeric(0)) # zero length data.frame
d_00 = data.frame(numeric(0)) # zero length data.frame without names
names(d_00) <- NULL # remove names to obtain value being an empty list()
at the end of Ops.data.frame
d_3 = data.frame(a=1:3) # non-empty data.frame
m_0 = matrix(logical(0)) # zero length matrix
#
# error A:
# Error in matrix(if (is.null(value)) logical() else value, nrow = nr,
dimnames = list(rn, :
# length of 'dimnames' [2] not equal to array extent
d_0 == 1 # error A
d_00 == 1 # <0 x 0 matrix>
d_3 == 1 # <3 x 1 matrix>
d_0 == logical(0) # error A
d_00 == logical(0) # <0 x 0 matrix>
d_3 == logical(0) # error A
d_0 == NULL # error A
d_00 == NULL # <0 x 0 matrix>
d_3 == NULL # error A
m_0 == d_0 # error A
m_0 == d_00 # <0 x 0 matrix>
m_0 == d3 # error A
# empty matrix for comparison
m_0 == 1 # < 0 x 1 matrix>
m_0 == logical(0) # < 0 x 1 matrix>
m_0 == NULL # < 0 x 1 matrix>
# All errors above could be solved by changing the last line in
Ops.data.frame from
# matrix(if (is.null(value)) logical() else value, nrow = nr, dimnames =
list(rn, cn))
# to
# matrix(if (length(value)==0) logical() else value, nrow = nr, dimnames
= list(rn, cn))
# Alternatively or in addition one could add an explicit test for
data.frame() == NULL if desired and raise an error
#
# non-empty return value but failing in the same code line due to
incompatible dimensions.
# should Ops.data.frame at all be dispatched for == object> ?
setClass("FOOCLASS",
representation("list")
)
ma = new("FOOCLASS", list(M=matrix(rnorm(300), 30,10)))
isS4(ma)
d_3 == ma # error A
##
Best regards,
Hilmar
Am 11/09/2019 um 13:26 schrieb Hilmar Berger:
Sorry, I can't reproduce the example below even on the same machine.
However, the following example produces the same error as NULL values
in prior examples:
> setClass("FOOCLASS",
+ representation("list")
+ )
> ma = new("FOOCLASS", list(M=matrix(rnorm(300), 30,10)))
> isS4(ma)
[1] TRUE
> data.frame(a=1:3) == ma
Error in matrix(unlist(value, recursive = FALSE, use.names = FALSE),
nrow = nr, :
length of 'dimnames' [2] not equal to array extent
Best,
Hilmar
On 11/09/2019 12:24, Hilmar Berger wrote:
Another example where a data.frame is compared to (here non-null,
non-empty) non-atomic values in Ops.data.frame, resulting in an error
message:
setClass("FOOCLASS2",
slots = c(M="matrix")
)
ma = new("FOOCLASS2", M=matrix(rnorm(300), 30,10))
> isS4(ma)
[1] TRUE
> ma == data.frame(a=1:3)
Error in eval(f) : dims [product 1] do not match the length of object
[3]
As for the NULL/logical(0) cases I would suggest to explicitly test
for invalid conditions in Ops.data.frame and generate a
comprehensible message (e.g. "comparison is possible only for atomic
and list types") if appropriate.
Best regards,
Hilmar
On 11/09/2019 11:55, Hilmar Berger wrote:
In the data.frame()==NULL cases I have the impression that the fact
that both sides are non-atomic is not properly detected and
therefore R tries to go on with the == method for data.frames.
From a cursory check in Ops.data.frame() and some debugging I have
the impression that the case of the second argument being non-atomic
or empty is not handled at all and the function progresses until the
end, where it fails in the last step on an empty value:
matrix(unlist(value, recursive = FALSE, use.names = FALSE),
nrow = nr, dimnames = list(rn, cn))
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