Format printing inside a matrix
On 7/7/19 17:41, Jialin Ma wrote:
Hi Abby, Thanks a lot for your paraphrasing and your suggestion! The problem of wrapping the list into a S3/S4 object, i.e. subclassing array or matrix, is that one also has to define a bunch of methods for subsetting, joining, etc, in order to make it behave like a list array. The reason is that most R functions for subsetting, joining, etc. do not preserve class attributes of the input, which is possibly by design.
Is it? One could argue that a more sensible behavior would be that things like `[`(..., drop=FALSE), rbind(), cbind(), etc... preserve the class attribute. Interestingly t() does that: m <- matrix(1:6, nrow=2) class(m) <- "foo" m # [,1] [,2] [,3] # [1,] 1 3 5 # [2,] 2 4 6 # attr(,"class") # [1] "foo" t(m) # [,1] [,2] # [1,] 1 2 # [2,] 3 4 # [3,] 5 6 # attr(,"class") # [1] "foo" but not aperm() (which in this case would be expected to be equivalent to t()): aperm(m, 2:1) # [,1] [,2] # [1,] 1 2 # [2,] 3 4 # [3,] 5 6 Reshaping also preserves the class: dim(m) <- c(6, 1) m # [,1] # [1,] 1 # [2,] 2 # [3,] 3 # [4,] 4 # [5,] 5 # [6,] 6 # attr(,"class") # [1] "foo" So if it makes sense for t() and reshaping, it's not clear why it wouldn't for [, aperm(), cbind(), etc...? H.
It is not desirable if a simple matrix subsetting will remove the class attributes of the object. There are also many other common functions that are meant to drop the attributes of the input, e.g. lapply, apply -- they are not generics and it is not wise to override them. Overall, introducing a new S3/S4 class often brings some extra price in order to maintain the correct behavior, which is why I tend to avoid them unless it is necessary. Best regards, Jialin On Sunday, July 7, 2019 4:43:59 PM PDT Abby Spurdle wrote:
contains an array of question marks, which isn't helpful. Would it be possible for the print method for both matrices and arrays (conditional on having a list type), call the format method for each object, possibly creating a character matrix? Presumably there are other approaches, but the main thing is that the output is useful and it's easy for R users to control the way objects (in matrices and arrays) are printed.
Or is there any other place that I can override without introducing a new
S3 class? In theory, the simplest approach is to redefine the print method for matrices. However, that would be unacceptable in a CRAN package, probably... So, unless R Core change the print method, you may have to create a matrix subclass.
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