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rmultidimensional-array
Max
Max

Reputation: 1800

"Axis" names for dimnames of multidimensional array in R

How do you label dimensions in an R array? (note: I don't mean "how do you label each point on the axis within each dimension!). For example, suppose I create the following matrix:

foo <- array(NA, dim = c(2, 2, 2), dimnames = list(c(1, 2), c(3, 4), c(5, 6)))

I would like the first dimension to be labelled "foo," the second dimension to be labelled "bar," and the third dimension to be labelled "baz" so that the user of foo can immediately see what each dimension represents.

A workaround I am aware of is to return data as a dataframe, using column names to label the various dimensions. For various reasons though, I would prefer to keep the data as denormalized (is that the right direction?) as possible.

Thanks!

Upvotes: 0

Views: 407

Answers (1)

MichaelChirico
MichaelChirico

Reputation: 34703

I would do the following:

dims = dim(foo)
dim_names = c("foo", "bar", "baz")

dimnames(foo) = 
  lapply(seq_along(dims), 
         function(ii)
           paste0(dim_names[ii], seq(to = cumsum(dims)[ii], 
                                     length.out = dims[ii])))

foo
# , , baz5
#
#      bar3 bar4
# foo1   NA   NA
# foo2   NA   NA
# 
# , , baz6
#
#      bar3 bar4
# foo1   NA   NA
# foo2   NA   NA

Upvotes: 1

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