On Sat, Jul 7, 2018 at 1:50 PM, Gabe Becker <becker.gabe at gene.com> wrote:> Hadley, > >> >> I was thinking primarily of completing the set of is.matrix() and >> is.array(), or generally, how do you say: is `x` a 1d dimensional >> thing? > > > Can you clarify what you mean by dimensionality sense and specifically 1d > here?What do we call a vector that is not an array? (or matrix) What do we call an object that acts 1-dimensional? (i.e. has length(dim()) %in% c(0, 1)) ?> You can also have an n x 1 matrix, which technically has 2 dimensions but > conceptually is equivalent to a 1d array and/or a vector.Yes. You can also have array that's n x 1 x 1.> Also, are you including lists in your conceptions of 1d vector here? I'm > with Duncan here, in that i'm having trouble understanding exactly what you > want to do without a bit more context.Isn't it standard terminology that a vector is the set of atomic vectors + list? Hadley -- http://hadley.nz
Hello, Inline. ?s 21:32 de 07-07-2018, Hadley Wickham escreveu:> On Sat, Jul 7, 2018 at 1:50 PM, Gabe Becker <becker.gabe at gene.com> wrote: >> Hadley, >> >>> >>> I was thinking primarily of completing the set of is.matrix() and >>> is.array(), or generally, how do you say: is `x` a 1d dimensional >>> thing? >> >> >> Can you clarify what you mean by dimensionality sense and specifically 1d >> here? > > What do we call a vector that is not an array? (or matrix) > > What do we call an object that acts 1-dimensional? (i.e. has > length(dim()) %in% c(0, 1)) ? > >> You can also have an n x 1 matrix, which technically has 2 dimensions but >> conceptually is equivalent to a 1d array and/or a vector. > > Yes. You can also have array that's n x 1 x 1.In which case it would be (length(dim(.)) - sum(dim(.) == 1)) %in% c(0, 1) Hope this helps, Rui Barradas> >> Also, are you including lists in your conceptions of 1d vector here? I'm >> with Duncan here, in that i'm having trouble understanding exactly what you >> want to do without a bit more context. > > Isn't it standard terminology that a vector is the set of atomic vectors + list? > > Hadley >
Thanks, Hadley for bringing this up:-) I am teaching R and I can suggest 5 different definitions of 'vector': a) vector as a collection of homogeneous objects, indexed by [ ] (more precisely atomic vector). Sometimes you hear that in R, "everything is a vector", but this is only true for atomic objects. b) vector as a collection of objects, indexed by either [ ] and [[ ]]. This includes atomic vectors and lists. c) vector versus scalar. It pops up when teaching math and stats, and is somewhat confusing, in particular if my previous claim was that "R does not have scalars". d) vector versus matrix (or other arrays). Again, it only matters when doing matrix operations where 'vectors', i.e. objects with NULL dimension, behave their own way. e) finally, 'is.vector' has it's own understanding what constitutes a vector. Maybe there are more... I don't think there are any easy answers but both me and my students would appreciate more consistent terminology. Cheers, Ott On Sat, Jul 7, 2018 at 1:32 PM, Hadley Wickham <h.wickham at gmail.com> wrote:> On Sat, Jul 7, 2018 at 1:50 PM, Gabe Becker <becker.gabe at gene.com> wrote: > > Hadley, > > > >> > >> I was thinking primarily of completing the set of is.matrix() and > >> is.array(), or generally, how do you say: is `x` a 1d dimensional > >> thing? > > > > > > Can you clarify what you mean by dimensionality sense and specifically 1d > > here? > > What do we call a vector that is not an array? (or matrix) > > What do we call an object that acts 1-dimensional? (i.e. has > length(dim()) %in% c(0, 1)) ? > > > You can also have an n x 1 matrix, which technically has 2 dimensions but > > conceptually is equivalent to a 1d array and/or a vector. > > Yes. You can also have array that's n x 1 x 1. > > > Also, are you including lists in your conceptions of 1d vector here? I'm > > with Duncan here, in that i'm having trouble understanding exactly what > you > > want to do without a bit more context. > > Isn't it standard terminology that a vector is the set of atomic vectors + > list? > > Hadley > > -- > http://hadley.nz > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel >[[alternative HTML version deleted]]
Hadley, On Sat, Jul 7, 2018 at 1:32 PM, Hadley Wickham <h.wickham at gmail.com> wrote:> On Sat, Jul 7, 2018 at 1:50 PM, Gabe Becker <becker.gabe at gene.com> wrote: > > Hadley, > > > >> > >> I was thinking primarily of completing the set of is.matrix() and > >> is.array(), or generally, how do you say: is `x` a 1d dimensional > >> thing? > > > > > > Can you clarify what you mean by dimensionality sense and specifically 1d > > here? > > What do we call a vector that is not an array? (or matrix) > > What do we call an object that acts 1-dimensional? (i.e. has > length(dim()) %in% c(0, 1)) ? >Right, or even (length(dim()) == 0 || sum(dim() > 1) <= 1) but that is exactly my point, those two(/three) sets of things are not the same. 1d arrays meet the second definition but not the first. Matrices and arrays that don't meet either of yours would still meet mine. Which definition are you proposing strictly define what a vector is? Before we have a function which performs the test we need to actually know what is being tested. So again I would mirror Duncan's question: What code do you have now or are you planning to write that needs to check this, and how would it feel about the various types of objects being discussed here? In other words, in what cases do you actually need to strictly check if something "is a vector"? Another completely unrelated way to define vector, btw, is via the vector interface (from what I recall this is roughly [, [[, length, and format methods, though I'm probably forgetting some). This is (more or less) equivalent to defining a vector as "a thing that can be the column of a data.frame and have all the base-provided machinery work".> You can also have an n x 1 matrix, which technically has 2 dimensions but > > conceptually is equivalent to a 1d array and/or a vector. > > Yes. You can also have array that's n x 1 x 1. > > > Also, are you including lists in your conceptions of 1d vector here? I'm > > with Duncan here, in that i'm having trouble understanding exactly what > you > > want to do without a bit more context. > > Isn't it standard terminology that a vector is the set of atomic vectors + > list? >Maybe. If by standard you mean commonly used/understood, though, I doubt most R users would understand a list to be a vector. I think most people think of atomic vectors exclusively when they hear "vector" unless they've very specifically been trained not to do so. Best, ~G> > Hadley > > -- > http://hadley.nz >-- Gabriel Becker, Ph.D Scientist Bioinformatics and Computational Biology Genentech Research [[alternative HTML version deleted]]
Gabe, I agree that If by standard you mean commonly used/understood, though, I doubt> most R users would understand a list to be a vector. I think most people > think of atomic vectors exclusively when they hear "vector" unless they've > very specifically been trained not to do so.However, a common way to create lists is by a construct like 'vector("list", n)'. Also, 'is.vector' reports TRUE for lists (but FALSE for many other vectors). This causes quite a bit of confusion, unless everyone understands the different 'vector' concepts, embedded in R. Cheers, Ott [[alternative HTML version deleted]]
On Sat, Jul 7, 2018 at 3:48 PM, Ott Toomet <otoomet at gmail.com> wrote:> Thanks, Hadley for bringing this up:-) > > I am teaching R and I can suggest 5 different definitions of 'vector': > > a) vector as a collection of homogeneous objects, indexed by [ ] (more > precisely atomic vector). Sometimes you hear that in R, "everything is a > vector", but this is only true for atomic objects. > b) vector as a collection of objects, indexed by either [ ] and [[ ]]. This > includes atomic vectors and lists. > c) vector versus scalar. It pops up when teaching math and stats, and is > somewhat confusing, in particular if my previous claim was that "R does not > have scalars". > d) vector versus matrix (or other arrays). Again, it only matters when > doing matrix operations where 'vectors', i.e. objects with NULL dimension, > behave their own way. > e) finally, 'is.vector' has it's own understanding what constitutes a > vector.Yes! And to add to the confusion there are three meanings to numeric vector: * As an alias for double (i.e. numeric() and as.numeric()) * To refer to integer and double types jointly (as is S3 and S4 class) * A vector that behaves as if it is a number (e.g. is.numeric(), which excludes factors) Hadley -- http://hadley.nz
On Sat, Jul 7, 2018 at 11:19 PM, Gabe Becker <becker.gabe at gene.com> wrote:> Hadley, > > > On Sat, Jul 7, 2018 at 1:32 PM, Hadley Wickham <h.wickham at gmail.com> wrote: >> >> On Sat, Jul 7, 2018 at 1:50 PM, Gabe Becker <becker.gabe at gene.com> wrote: >> > Hadley, >> > >> >> >> >> I was thinking primarily of completing the set of is.matrix() and >> >> is.array(), or generally, how do you say: is `x` a 1d dimensional >> >> thing? >> > >> > >> > Can you clarify what you mean by dimensionality sense and specifically >> > 1d >> > here? >> >> What do we call a vector that is not an array? (or matrix) >> >> What do we call an object that acts 1-dimensional? (i.e. has >> length(dim()) %in% c(0, 1)) ? > > > > Right, or even (length(dim()) == 0 || sum(dim() > 1) <= 1) > > but that is exactly my point, those two(/three) sets of things are not the > same. 1d arrays meet the second definition but not the first. Matrices and > arrays that don't meet either of yours would still meet mine. Which > definition are you proposing strictly define what a vector is?I am not proposing any definition. I am enquiring if there is a definition in base R. The answer appears to be now.> Another completely unrelated way to define vector, btw, is via the vector > interface (from what I recall this is roughly [, [[, length, and format > methods, though I'm probably forgetting some). This is (more or less) > equivalent to defining a vector as "a thing that can be the column of a > data.frame and have all the base-provided machinery work".I don't know if that definition is adequate because a call would be a vector by that definition. I'm pretty sure a call does not make sense as a data frame column. Also technically data frames don't require their columns to have equal length(), but equal NROW(). So the spirit of that definition would imply that a matrices and arrays are also vectors, which seems like it might be undesirable. Hadley -- http://hadley.nz